Power converter circuitry and method

ABSTRACT

A control system and method for simultaneously regulating the operation of a plurality of different types of switching power converters. The system utilizes in regulating the power converters sampled data and nonlinear feedback control loops.

FIELD OF THE INVENTION

[0001] This invention relates to switching power supplies or converters.In particular, this invention relates to a simple, robust switchingpower supply which is capable of providing power to a number ofdifferent regulated power sources within a given circuit.

BACKGROUND OF THE INVENTION

[0002] Switching power supplies are used to provide power in numerousproducts such as cell phones, camera, PDAs (Personal DigitalAssistants), calculators, portable computers and similar types ofelectronic equipment. Such switching power supplies are quite complexand use numerous components to provide a number of precisely regulatedoutput voltages to power the various integrated circuits and othercomponents contained within the product being powered. Relative to thecost and the quality of the products in which they are used, such powersupplies are expensive, bulky and inefficient. Efficiency is importantto provide the equipment a long battery life. FIG. 1 shows a typicalprior art power supply used in portable equipment powered by a battery10. The signal from battery 10 is transmitted on lead 10 a to a leveltranslation circuit 12, which is controlled by a control signal fromanalog pulse width modulated controller 11. The control signal fromanalog pulse width modulator is responsive to the voltage drop acrossresistor 16 as detected by signals on conductive leads 17 a and 17 bconnecting, respectively, the two terminals of resistor 16 into analogPWM controller 11. N-channel MOS transistors 13 a and 13 b are connectedto operate in a complementary fashion. Level translation circuit 12provides a high level voltage to the gate of N-channel transistor 13 ato apply a pulse from battery 10 to one input terminal of coil 15. Theother input terminal of coil 15 is connected to one terminal of resistor16. The other terminal of resistor 16 is connected to load capacitor 18,which contains a charge at the voltage necessary to supply theparticular circuitry being powered by this portion of the power supply.The analog PWM controller 11 measures the current through resistor 16and controls the ON time of N-channel MOS transistor 13 a. N-channel MOStransistor 13 b is driven by the complement of the signal driving thegate of N-channel MOS transistor 13 a and turns on to pull the inputlead of coil 15 to ground and to shut off the current required to besupplied through resistor 16 to the power supply. Internal circuitry ofanalog pulse width controller 11 is shown schematically in FIG. 2.

[0003] As shown in FIG. 2, current source 20 provides a charging currentto capacitor 21 to generate a ramp voltage across this capacitor. Thisramp voltage is provided to the positive input lead of differentialamplifier 22 a, the negative input lead of which receives the outputsignal from differential amplifier 22 b. The positive input lead ofamplifier 22 b is connected to the load capacitor 18 and carries asignal representing the voltage across the load capacitor 18. Thenegative input lead of differential amplifier 22 b is connected to thenode between resistors 23 a and 23 b making up a voltage divider (oneterminal of which is connected to a reference voltage VRef and the otherterminal of which is connected to the output lead of differentialamplifier 22 b). Thus when the output voltage across capacitor 18 isless than the voltage at node A between resistor 23 a and resistor 23 b,the output voltage from differential amplifier 22 b goes to a low level.This low level output voltage is provided to the negative input lead ofamplifier 22 a, causing amplifier 22 a to produce a positive outputpulse. This positive output pulse is transferred to coil 15 to provide acharging current to capacitor 18. With time, the charge on capacitor 18increases until the voltage across capacitor 18 exceeds the voltage onnode A. At this point the output voltage from differential amplifier 22b goes to a high level, so that the voltage at the negative input leadof differential amplifier 22 a exceeds the voltage on the positive inputlead of differential amplifier 22 a, causing the output voltage fromamplifier 22 a to go a low level, and thus preventing further chargingof capacitor 18. The voltage across coil 15 is negative, reflecting thenegative rate of change in current in response to the trailing edge ofthe pulse from amplifier 22 a going from a high level to a low level.The current through coil 15 does not change instantaneously due to themagnetic field of the coil but rather gradually changes with time. Thistype of power supply, which is characterized by a current source drivinga capacitor, is known as an analog buck converter. Each MOSFETmodulation cycle is formed by the precision comparator and the erroramplifier. Such a power supply is difficult to scale and integrate intoan integrated circuit and is typically fabricated using dedicated analogprocess technologies at captive semiconductor foundries.

[0004] Accordingly, what is needed is a power supply which providesdifferent level precision voltages and at the same time and is simple toimplement with a smaller number of components than in the prior art.Such a power supply must also be relatively inexpensive, robust andreliable.

SUMMARY OF THE INVENTION

[0005] In accordance with this invention a switching power supply isprovided which is both inexpensive and robust and at the same timecapable of providing a number of different output voltages.

[0006] In accordance with one embodiment of this invention, a ringoscillator is used together with a switching matrix to provide a pair ofsignals, which are then used to generate a pulse width modulated signalto control the current through an inductor and thereby the voltageacross an output capacitor in a power supply. The particular pair ofsignals from the ring oscillator selected to generate the pulse widthmodulated signal is determined by a controller which detects the voltageacross the output capacitor and provides a sufficient current tomaintain the desired voltage across the output capacitor. The outputcapacitor supplies the circuit being driven by the power supply withcurrent at a selected voltage. The duty cycle of the pulse widthmodulated signal can be controlled from 0 to a value of almost 100%. Thering oscillator includes an odd number of inverters and the larger thenumber of inverters the closer the duty cycle can come to 100%. A phasecomparator locks the frequency of the oscillation of the ring oscillatorto a desired value.

[0007] In an alternative embodiment, an n-bit counter is used togenerate two signals, one time-offset from the other such that the delaybetween these two signals controls the width of the pulse output from apulse width modulator. In one embodiment, the structure includes twodigital comparators each driving a flip-flop which produces an outputsignal-delayed by the time delay in each comparator.

[0008] The circuitry of this invention can control the voltage levels ofa number of different power supplies. In particular, the availability ofdifferent taps on the ring oscillator allows different pairs of signalsto be selected with each pair used to produce a separate pulse widthmodulation signal in response to the voltage across a correspondingoutput capacitor varying from the desired norm. Thus a single controllerin accordance with this invention can control a plurality of powersupplies in a system, each of which supplies a different voltage.

[0009] The pulse width modulation control circuit of this invention iseconomical, easily fabricated on an integrated circuit substrateutilizing standard process technologies available at merchantsemiconductor foundries and capable of numerous uses in applicationswhere pulse width modulated output signals are required.

[0010] According to one embodiment of the present invention, apredictive control loop is provided to regulate one or more outputvoltages. The predictive control loop may use a computational element(e.g., a microcontroller) to apply digital control techniques toregulate the output voltages. In one embodiment, the duty cycles ofsignals drive switches in a pulse-width modulated converter to vary thecurrent in an external inductor, in response to a variation in theconverter's output voltage. In one control technique according to thepresent invention, using a linear circuit model of the converter, theconverter predicts the converter's response to a change in outputvoltage (e.g., when a load is switched on), and applies non-linearcorrections over multiple time steps. In one embodiment, the converterseeks to restore the converter to an equilibrium state in which theoutput voltage is restored, the average current in the inductor (“coilcurrent”) is the average current in the load, and the coil current doesnot change from time step to time step.

[0011] This invention will be more fully understood in conjunction withthe drawings taken together with the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 shows the basic construction of a prior art analog buckconverter.

[0013]FIG. 2 shows the details of the analog PWM controller 11 in FIG.1.

[0014]FIG. 3 shows the basic structure of a pulse width modulationcontroller utilizing a ring oscillator in accordance with thisinvention.

[0015]FIG. 4 shows an alternative implementation of a pulse widthmodulated controller in accordance with this invention.

[0016]FIG. 5 shows an example of waveforms of the type generated usingthe structure of FIG. 3.

[0017]FIG. 6 shows a ring oscillator used in accordance with thisinvention together with a switching matrix used to select the particularoutput signals from the ring oscillator to be provided to the two inputleads of an exclusive OR gate 63 to generate a pulse width modulatedsignal.

[0018]FIG. 7 shows the waveform of signals generated using the structureof FIG. 6.

[0019]FIG. 8 shows the waveforms generated using the structure of FIG. 6with an inverter connected between the output lead from eacheven-numbered inverter in the ring oscillator and the pass-transistorsdriven by the signals G, H, I, J and K.

[0020]FIG. 9 shows the relative delay times obtained when signals areselected from different combinations of pairs of inverters in the ringoscillator of FIG. 6.

[0021]FIG. 10 shows one circuit for controlling the selection of theparticular gates to transfer a selected pair of signals to the exclusiveOR gate 63 in FIG. 6 to generate a pulse width modulated signal.

[0022]FIG. 11 shows another circuit used to generate the pulse widthmodulated signal from exclusive OR gate 63 in FIG. 6 in accordance withthe principles of this invention

[0023]FIG. 12 is a block diagram of switching power supply controller1200, in accordance with one embodiment of the present invention.

[0024]FIG. 13 is a block diagram showing interface signals of digitalpulse converter wrapper 1201, according to one implementation.

[0025]FIG. 14 is a block diagram showing interface signals of analog todigital converter 1206, according to one implementation.

[0026]FIG. 15 is a block diagram showing the interface signals of Kelvintemperature sensor (KTS) 1500.

[0027]FIG. 15A is an exemplary circuit for KTS 1500 in accordance withone implementation.

[0028]FIG. 16 is a timing diagram illustrating the quad-slope (i.e.,dual conversion) analog to digital conversion (ADC) operations carriedout in the QSADC module 1211 a, which is contained within touch screeninterface 1211.

[0029]FIG. 17 is a block diagram showing the interface signals of QSADCmodule 1211 a in one implementation.

[0030]FIG. 17A is a block diagram showing the interface signals of QSADC1211 a with touch screen interface 1211 in one implementation.

[0031]FIG. 18 is a top-level block diagram of QSADC module 1211 a,including analog block ANLG 1801, control block CNTRL 1802 and DOWN/UPCOUNTER block 1803, according to one embodiment of the presentinvention.

[0032]FIG. 18A shows one implementation of analog block 1801 of QSADmodule 1211 a shown in FIG. 18.

[0033]FIG. 18B shows one arrangement of a four-contact touch-screenapplication.

[0034]FIG. 18C shows one arrangement of a five-contact touch-screenapplication.

[0035]FIG. 19 is a block diagram summarizing the modules in switchingpower supply controller 1200, providing a control loop for a battery orpower supply management application.

[0036]FIG. 20 illustrates regulation of output voltage Vout usinginductor current IL and sensing output voltage Vout, according to oneembodiment of the present invention.

[0037]FIG. 21 illustrates the approximation of a weighted averageinductor current by duty cycle.

[0038]FIG. 22 illustrates a method under the present invention forestimating the parasitic resistance of an MOS switch.

[0039]FIG. 23 shows flow diagram 2300, illustrating a control methodaccording to one embodiment of the present invention.

[0040]FIG. 24 illustrates a low-frequency closed loop and high-frequencyopen loop control method, according to one embodiment of the presentinvention.

[0041]FIG. 25 is a diagram showing switching power supply controller1200 being used in a battery and power supply management application in,for example, a personal digital assistant (PDA).

[0042]FIG. 26 illustrates the operation of a control loop in accordanceof the present invention.

[0043]FIG. 27 illustrates the low-frequency closed loop andhigh-frequency open loop control method of FIG. 24, showing thesignature input values of controlled variables and an open-loopresponse, according to one embodiment of the present invention.

[0044]FIG. 28 illustrates a sequential transient recovery controlmethod, in accordance with one embodiment of the present invention.

[0045]FIG. 29 illustrates a buck converter.

[0046]FIG. 30 through FIG. 33 show curves of current with respect totime for a supply circuit such as circuit 49, based on the applicationof different gate drive voltages to the transistors.

[0047]FIG. 34 is a block diagram showing the interface signals of clockgenerator 12223.

[0048]FIG. 35 shows the port table for the clock generator block shownin FIG. 34 and FIG. 12.

[0049]FIG. 36 shows an exemplary pulse width modulation implementation,which includes a pulse width generator and a sequencer, for digitalpulse converter 1201.

[0050]FIG. 36A is an exemplary implementation of the pulse widthgenerator of FIG. 36.

[0051]FIG. 36B is an exemplary implementation of the sequencer of FIG.36.

[0052]FIG. 36C shows an exemplary feedback control system.

[0053]FIG. 36D shows another exemplary feedback control system.

[0054]FIG. 37 shows a timing diagram for one digital to pulse converterframe for DPC 1201 in accordance with one implementation.

[0055]FIG. 37A shows exemplary interface signals for digital pulseconverter 1201 for one implementation.

[0056]FIG. 37B illustrates an exemplary circuit implementation for DPC1201, which includes a CAM.

[0057]FIG. 37C illustrates one exemplary implementation for the CAM ofFIG. 37B.

[0058]FIG. 37D illustrates an exemplary circuit implementation foroutput logic of the CAM of FIG. 37C.

[0059]FIG. 37E illustrates an exemplary timing diagram for the CAM ofFIG. 37C.

[0060]FIG. 38 shows an exemplary implementation of a Grey counter.

[0061]FIG. 38A shows another exemplary implementation of a Grey counter.

[0062]FIG. 38B shows an exemplary implementation for a flip flop of FIG.38 or FIG. 38A.

[0063]FIG. 38C shows an exemplary implementation for another flip flopof FIG. 38 or FIG. 38A.

[0064]FIG. 38D shows an exemplary circuit implementation for a logicgate.

[0065]FIG. 38E shows an exemplary circuit implementation for anotherlogic gate.

[0066]FIG. 38F shows an exemplary circuit implementation for amultiplexer.

[0067]FIG. 38G shows an exemplary circuit implementation for binary toGrey and Grey to binary conversion.

[0068]FIG. 38H illustrates an exemplary implementation for a digitalpulse converter.

[0069]FIG. 38I illustrates another exemplary implementation for adigital pulse converter.

[0070]FIG. 39 shows a plot of typical gate drive waveforms which may beapplied to, for example, the gates of the transistors of circuit 49 andthe resulting voltage at terminal S.

[0071]FIG. 40 is a block diagram of SHM 1207 in one implementation.

[0072]FIG. 40A is a functional schematic illustrating voltage andcurrent sampling for one implementation.

[0073]FIG. 40B is a circuit schematic illustrating voltage and currentselection for one implementation.

[0074]FIG. 40C is an exemplary interface signal block for SHM 1207 inaccordance with another implementation.

[0075]FIG. 40D is a block diagram of SHM 1207 in another implementation.

[0076]FIG. 40E is a functional schematic illustrating voltage andcurrent sampling for another implementation.

[0077]FIG. 40F is a circuit schematic illustrating voltage and currentselection for another implementation.

[0078]FIG. 40G is a clock generation circuit in accordance with anotherimplementation.

[0079]FIG. 40H is a voltage divider in accordance with anotherimplementation.

[0080]FIG. 40I is a voltage multiplier in accordance with anotherimplementation.

[0081]FIG. 40J is an exemplary interface signal block for an I/O circuitin accordance with another implementation.

[0082]FIG. 40K is a multiplexer scheme in accordance with anotherimplementation.

[0083]FIG. 41 is a block diagram of the regulation control module (REG)of FIG. 12 according to one embodiment of the invention.

[0084]FIG. 42 shows a gate drive waveform with respect to time.

[0085]FIG. 42A shows a boost converter circuit.

[0086]FIG. 42B shows two switching waveform in time off-setrelationship.

[0087]FIG. 43 shows waveform A, B and C illustrating the current whichis output for three gate drive scenarios of a switching power supply.

[0088]FIG. 43A shows a plot of the voltage with respect to time at aterminal S intermediate the upper and lower transistors in buckconverter 49 of FIG. 29.

[0089]FIG. 43B and FIG. 43C show plots of the voltage at terminal S fortwo different duty cycles of FET 50 in circuit 49.

[0090]FIG. 44 shows a circuit for generating a high voltage to drive acold cathode fluorescent light bulb.

[0091]FIG. 44A shows two exemplary sets of gate drive waveforms of thetype which could be applied to the gates of the transistors of circuit1.2.2.12.

[0092]FIG. 45 shows a buck converter circuit.

[0093]FIG. 45A shows gate drive waveforms for the transistors in FIG. 45and corresponding current and output voltage waveforms.

[0094]FIG. 45B shows a boost circuit.

[0095]FIG. 45C shows gate drive waveforms for the circuit of FIG. 45Band corresponding current and output voltage waveforms.

[0096]FIG. 46 shows switching power supply controller 1200 connected toregulate the operation of two switching power supplies.

[0097]FIG. 46A shows a plot of current with respect to time for onecycle of a switching power supply.

[0098]FIG. 46B shows a buck power supply circuit.

[0099]FIG. 46C shows a plot of current with respect to time for onecycle of a switching power supply circuit.

[0100]FIG. 46D shows a plot of current with respect to time for onecycle of a switching power supply.

[0101]FIG. 46E shows a plot of current with respect to time for aswitching power supply circuit.

[0102]FIG. 47 shows switching power supply controller 1200 connected toa plurality of power supplies.

[0103]FIG. 48 shows in block diagram form a processor coupled to twoswitching supplies, a nonvolatile memory and a Kelvin temperaturesensor, with a battery connected to one of the switching power supplies.

[0104]FIG. 48A shows a curve of battery capacity with respect totemperature for a typical battery.

[0105]FIG. 49 shows a block diagram of a power supply system for use inconjunction with a cellular telephone.

[0106]FIG. 49A shows a block diagram for a solar cell array coupled to apower supply being controlled by switching power supply controller 1200of the present invention.

[0107]FIG. 50 is a block diagram of a spreader divider unit 2482.4according to one embodiment of the invention.

[0108]FIG. 50A is a circuit diagram of a spectral spreader 210.1 for thespreader divider unit 2482.4 of FIG. 50 according to one embodiment ofthe invention.

[0109]FIG. 51 is a block diagram showing the interface signals of QSADCmodule 1211 b in another implementation.

[0110]FIG. 51A is a top-level block diagram of QSADC module 1211 b,including analog block 2001.4, control block 2002.4, and up/down counterblock 2003.4, according to another embodiment of the present invention.

[0111]FIG. 51B shows one implementation of analog block 2001.4 of FIG.51A.

[0112]FIG. 51C illustrates a block diagram showing exemplary interfacesignals between touch screen interface 1211 and the other blocks ofswitching power supply controller 1200.

[0113]FIG. 51D shows a flowchart for performing diagnostics of QSADCmodule 1211 a.

[0114]FIG. 51E shows a functional block diagram corresponding to theimplementation of FIG. 51B.

[0115]FIG. 51F illustrates the circuit connections of analog block 1801for an initial measurement state.

[0116]FIG. 51G illustrates the circuit connections of analog block 1801to integrate the voltage due to contact with the Y coordinate sheet in afour-contact implementation.

[0117]FIG. 51H illustrates the circuit connections of analog block 1801to digitally convert the voltage due to contact with the Y coordinatesheet in a four-contact implementation.

[0118]FIG. 51I illustrates the circuit connections of analog block 1801to integrate the voltage due to contact with the X coordinate sheet in afour-contact implementation.

[0119]FIG. 51J illustrates the circuit connections of analog block 1801to digitally convert the voltage due to contact with the X coordinatesheet in a four-contact implementation.

[0120]FIG. 51K illustrates the circuit connections of analog block 1801to integrate the voltage due to contact with the X-Y coordinate sheet ina five-contact implementation due to horizontal position.

[0121]FIG. 51L illustrates the circuit connections of analog block 1801to digitally convert the voltage due to contact with the X-Y coordinatesheet in a five-contact implementation due to vertical position.

[0122]FIG. 51M illustrates the circuit connections of analog block 1801to integrate the voltage due to contact with the X-Y coordinate sheet ina five-contact implementation due to horizontal position.

[0123]FIG. 51N illustrates the circuit connections of analog block 1801to digitally convert the voltage due to contact with the X-Y coordinatesheet in a five-contact implementation due to horizontal position.

[0124]FIG. 51O illustrates the circuit connections of analog block 1801to detect continuity between the resistive sheets in a four-contactimplementation.

[0125]FIG. 51P illustrates the detection of contact for a five-contactimplementation.

[0126]FIG. 52 illustrates a block diagram of LED control block 1214.

[0127]FIG. 53 is a block diagram for the watchdog module of FIG. 12according to one embodiment of the invention.

[0128]FIG. 54 is an exemplary functional diagram of Internal VoltageSupply (IVS) 1209 in accordance with one implementation.

[0129]FIG. 54A is an exemplary interface block diagram for IVS 1209 inaccordance with another implementation.

[0130]FIG. 54B is another exemplary functional diagram of IVS 1209 inaccordance with another implementation.

[0131]FIG. 54C is an exemplary flowchart for a power-up sequence for IVS1209 in accordance with another implementation.

[0132]FIG. 55 is an exemplary functional diagram of NFET driver module1202 in accordance with one implementation.

[0133]FIG. 55A illustrates exemplary interface signals of NFET drivermodule 1202 in accordance with another implementation.

[0134]FIG. 55B illustrates exemplary interface signals of NFET drivermodule 1202 in accordance with another implementation.

[0135]FIG. 55C shows an exemplary functional diagram for theimplementation of FIG. 55B.

[0136]FIG. 55D illustrates an application employing internal buffers todirectly drive an external coil for the implementation of FIG. 55B.

[0137]FIG. 55E illustrates an application employing internal buffers todrive external FETs for the implementation of FIG. 55B.

[0138]FIG. 55F shows an exemplary on-chip configuration block diagramfor the implementation of FIG. 55B.

[0139]FIG. 56 is a block diagram of central processing module (SYS) 1205of FIG. 12 according to one embodiment of the invention.

[0140]FIG. 57 shows a circuit model of converter 2570 of FIG. 25.

[0141]FIG. 58 is a flow chart illustrating the steps of controlalgorithm 5800, in accordance to with one embodiment of the presentinvention.

[0142]FIG. 59 illustrates the operation of control algorithm 5800 ofFIG. 58.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

[0143] The following detailed description is intended to illustrate theembodiments discussed herein and is not intended to be limiting of thescope of the present invention. Other embodiments of this invention willbe apparent to those skilled in the art in view of this disclosure.

Section 1.0 Overview of the Architecture of a Converter (DigitallyTrimmed Multi-Stage SPS) Having a Synchronous Sampling Multiple-OutputController, Functional Description of Each Block

[0144] The present invention is applicable to a power converter andpower management peripheral that integrates a set of power-managementrelated functions. Switching power supply controller 1200, shown in FIG.12 in block diagram form, illustrates an implementation of a switchingpower converter controller product, according to one embodiment of thepresent invention. The system implements substantially all of a powerconverter's expected functions, such as maintaining a steady outputvoltage (constant voltage power supply) that is substantiallyindependent of the current drawn from the power supply or maintaining asteady output current (constant current power supply) that issubstantially independent on the load applied to the power supply,deciding when to shed loads, and measuring the state of charge in abattery, charging the battery, and performing battery sequencing. Inaddition, the system performs a number of other peripheral managementfunctions, such as digitizing a touch panel, scanning a keyboard, andconditioning reset signals received from the rest of the system. In oneembodiment, watch dog timer functions are provided to allowpower-cycling and to provide reset signals to different subsystems ofthe product, in response to an exception condition, such as a softwarelock up or even a hardware lock up (e.g., an SCR latch up or adisruption due to an IO transient). The system of the present inventionalso controls LEDs that indicates the statuses of various subsystems.Thus, a system according to the present invention can handle a largenumber of functions that a portable electronic device (e.g., a PDA)performs when the processor of that PDA is powered down, such as betweenpen strokes (while the user is writing a note on the PDA), or when thePDA is displaying information, but no input or output is expected. Inthis implementation, the product includes a digital control subsystemthat controls various digital interfaces, including reset signals, watchdog timers, enable signals, status signals for indicating individualstatus of internal power supplies. Communication among elements of thesystem is provided through a communication interface. In one embodiment,the present invention includes a time base generation circuit and adigitizer interface to a keyboard.

[0145] Referring to FIG. 12, substantially all of the digital interfacefunctions are performed by an internal 8051 or a comparablemicroprocessor which is included in central processing module (SYS) 1205and which communicates with the outside system with a number ofinterfaces through a number of general purpose input/output (GPIO)signals that can be defined in software in the microprocessor and mappedflexibly to individual input or output pins or terminals of theintegrated circuit. For example, each pin can be defined to carry a hightrue or a low true signal, and can be defined to be an input signal oran output signal. In addition, each pin can be assigned to any of theindividual power supply elements and can be shared so that more than onepower supply can receive the same control signal from a single pin. Inthis manner, for example, a single enable signal may be shared amongstmultiple power supplies. The GPIO signals can be used to implement inputand output signals of some of the peripheral devices. For example, thekeyboard scanner functions interact with an external keyboard throughthe GPIO signal interface. The watchdog timer may receive input signalsand status information from circuits external to the integrated circuit.Also, interrupt signals can share pins with the GPIO signals. Thisimplementation thus provides a rich set of functionality to allow theproduct to be capable of being made “plug-compatible” with prior artsolutions that were based on separate discrete devices. Centralprocessing module (SYS) 1205 handles serial communication on and off thechip. Every signal which can be implemented as a GPIO signal, except aninterrupt signal, can also be implemented as a serial communicationsignal. In an application designed for prior art devices, serialcommunication can be used to access a keyboard and coulombmetricmeasurement capabilities. The GPIO signals can be used to turn on andoff individual power supplies and to monitor their statuses.

[0146] A computation circuit, which may be provided as a very longinstruction word processor (“VLIW engine”) to simplify decoding logic,is included in regulation control module (REG) 1204 (labelled in FIG. 12as “REG”). The VLIW engine executes low level commands from centralprocessing module (SYS) 1205 (labeled in FIG. 12 as “SYS”). Regulationcontrol module (REG) 1204 receives and interprets the measurements ofvoltages and currents from the various circuits supplied by theregulated power supply pins. Using a number of different types ofcontrol loops, regulation control module (REG) 1204 provides to digitalpulse converter (DPC) 1201 commands in the form of precisely modulatedsignals, which then are used to operate external components through NFETdriver module 1202. Together with the external components, switchingpower supply controller 1200 forms one or more power converters ofvarious designated topologies.

[0147] One unique feature of the system according to the presentinvention is that the system is programmable. In addition to allowingevery function, mode and regulation parameters to be preset, thespecifications of external components can be stored internally in theintegrated circuit and used to perform the regulator functions. Thus,regulation control module (REG) 1204 operates with a large amount ofinformation about the characteristics of the power converter componentsexternal to switching power supply controller 1200. Unlike a prior artswitching power supply controller circuit implemented in analogtechnology, a power supply controller circuit of the present invention“knows”the output voltage it's trying to attain (“target voltage”) andthe error(i.e., the difference between the current output voltage andthe target voltage). Typically, prior art analog converters correct theerror using algorithms that are independent of the current switchingduty cycle or the value of the input voltage. Such prior art convertersalso do not internally store information about the external components.An engineer attempting to design with such a prior art power supplycontroller circuit can only provide “hints” to the power supplycontroller circuit in the form of compensation networks. In contrast, apower supply controller circuit according to the present invention hasmany advantages and benefits over the prior. For example, havinginformation regarding the current output voltage and duty cycle, thetarget voltage and the internally stored parameter values of theexternal circuit allows the power supply controller to calculate thepotential duty cycles that would result in the correct output voltage tohigh precision and to select a realistic response that observes theconstraints of the external circuit (e.g., the saturation current of aninductor). Proper response to external circuit anomaly limits the amountof noise that's reflected to the power supply controller circuit. Forexample, by controlling the transient noise currents through the powercontroller circuit, a battery or a long wire that provide the supplyvoltage to the power controller circuit could experience and possiblyradiate less electromagnetic interference (EMI).

[0148] A programmable keyboard scan function is implemented in centralprocessing module (SYS) 1205, and allows individual keys to be scannedor detected after a key has been pressed to awake the keyboard scanningcircuit from a stand-by state. A watch dog function is performed withsoftware in central processing module (SYS) 1205, and providesfull-featured watch-dog timer functions. Watch dog timer functions maybe used to handle software faults in a system. For example an externalprocessor running a complex operating system (e.g., Win CE) mayperiodically briefly assert (“toggle”) a signal on a specified pin. Thewatch dog timer resets its timer whenever the signal on the specifiedpin is toggled. When a malfunction occurs in the software of the hostmicroprocessor, such that the signal on the specified pin is not toggledwithin the scheduled time, then a set of pre-programmed actions aretaken to recover operation of the external system processor. Theseactions range from simply resetting the processor or another circuitelement, or cycling the processor's power off and on. Power-cyclingremoves current from parasitic SCRs that may be present in the processoror other integrated circuits, thereby affecting a recovery from asemiconductor latch-up state. Other anomalies that would normally not berecoverable using logic or reset signals may also be corrected throughpower cycling.

[0149] Central processing module (SYS) 1205 controls external statusLEDs, or a single multi-color LED. Internal reset logic which isincluded in internal voltage supply 1209, provides a power-on reset toallow internal clocks and internally generated voltages to stabilizeprior to operation. This is a different and distinct concept from thehost reset conditioning feature described below, which is implemented insoftware and runs on the internal microcontroller. The host resetconditioning software conditions the external system's reset signal withthe status signals of the power supplies, and external signals at theproduct's input pins.

[0150] Touch screen interface 1211 uses a dual-slope technique to readthe X and Y coordinates of a resistive touch panel display. In a PDA,this digitization operation, because of the large area of the display,is quite subject to noise induced by the back light. In the prior art, atypical back light is implemented by cold cathode fluorescent light(CCFL), which is essentially a fluorescent light bulb that does not havea cathode heater to raise the energy of the internal gas for ionizationat a low voltage. In CCFL, for a typical device, initial ionization(“ignition”) is brought about using an AC voltage of 700 volts or more,and an AC voltage of over 300 volts is used thereafter to maintain theignition. The high voltage AC waveform that is driving the CCFL is apotentially serious source of noise to the touch panel, which is made upof panels of resistive material and is located only a few millimetersaway directly in front of the display. Touch screen interface 1211 usesa quad-slope analog-to-digital converter circuit which operatessynchronously with the back light voltages generated by the power supplycontroller. By operating synchronously with the back light, the noisefrom the back light is integrated over an even number of cycles, therebyeffectively removing it without a of complex filtering or an algorithmicapproach.

[0151] Internal voltage supply 1209 is the power supply for switchingpower supply controller 1200, deriving from either one of two externalsupply pins, or one of two external battery pins the internal voltagesrequired for the operations of the various blocks, including centralprocessing module (SYS) 1205 and regulation control module (REG) 1204.In addition to providing the various voltages required for the varioussubsystems, internal voltage supply 1209 also provides the crystaloscillator function (other than the crystal, which is off-chip) variouscharge pumps for creating internal supplies, and comparators to indicatewhen the supplies are stable for use by internal processing elements.

[0152] Sample and hold module 1207 includes an array of sample and holdcircuits and scaling circuits. Sample and hold module 1207 monitors thevarious points within the output sections of the power supplies,measuring voltages and currents, input voltages, and temperatures atvarious points. Sample and hold module 1207 provides its data, onesample at a time, to analog to digital converter 1206 (a system sharedresource), which converts the external analog samples into digitalsamples. The digital samples are used by regulation control module (REG)1204, or passed upstream to central processing module (SYS) 1205. Inthis embodiment of the present invention, the analog to digitalconverter and the sample and hold structures are based on either ratiosof capacitors or unity gain. Thus, calibration can be achieved using asingle calibration.

[0153] NFET drivers module 1202 include a set of output drivers whichoperate in one of two modes. The first mode is to drive external powerMOSFET devices. In this mode, each output voltage is associated with twosets of driver circuits; one for driving the control FET and the otherone for driving the sync FET. For modest currents, the two drivercircuits may be used in another mode of operation where they are driventogether, and their output signals may be connected together, to drivean external coil directly in a power switching function.

[0154] A power supply utilizing the present invention can be completelyprogrammable, i.e., no external discrete components have to be chosen toset voltages and currents and a single chip can perform many differentfunctions across many different products. Such programmability has thebenefit of reducing the component count on a circuit board. It also hasthe benefit of reducing the number of parts that an individualmanufacturer of an end product would have to stock since this samedevice can be used across many different applications. All of thesefeatures can be preset, either at the time the chip is manufactured, atthe time that it is delivered, i.e., through a distributor, usingprogramming techniques similar to those used with programmable logicarray devices. Alternatively, the system of the present invention can beprogrammed by a customer even on the circuit board during the in-circuittest phase or final test for their product. Further, even though allthese functions can be programmed, the values programmed duringmanufacturing and test are used merely as initial conditions and may bechanged dynamically (i.e., during operation) by the system containingthe power supply controller. For example, the system can reprogram theinternal voltages and currents dynamically, as is often required incomplex microprocessors which require different voltages for differentmodes of operation. Reprogramming activity can also be done for thepurposes of dimming displays and controlling motors. Digital-to-analogconversion functions can be implemented by rapidly changing the outputvoltages of the regulators. Switching power supply controller 1200features a completely programmable start-up and shut-down sequence, soas to allow a system using power supply controller 1200 to be started ina sequence that would avoid a latch-up conditions. For example, the I/Ostructure of a microprocessor is often required be powered before themicroprocessor core. To reverse the order could result in damage ordestruction of the microprocessor or cause a malfunction. A specificpower sequence is also required for powering down these devices. Inprior art solutions, this timing is set rather crudely by resistors andcapacitors or not at all.

[0155] The individual power supplies controlled by switching powersupply controller 1200 can be programmed for a wide variety oftopologies, so that if a voltage which is higher than the input source,lower than the input source, or sometimes the same as the input sourcecan be accommodated. For example, a boost converter topology is used fora power supply having an output voltage that is higher than the inputvoltage, a buck converter topology is used for a power supply having anoutput voltage that is lower case than the input voltage, and a sepictopology is used for a power supply having the same input and outputvoltages. When very high voltages are required (i.e., a cold cathodefluorescent light bulb or even a photographic strobe in a digitalcamera), topologies such as half-bridge may be used. All of these can beprogrammed and any number of them can be present in the design at anytime, and any combination of these topologies may be supportedsimultaneously.

[0156] Switching power supply controller 1200 of the present inventioncan also perform dimming using pulse width modulation. This ability isimportant for cold cathode fluorescent lights because, typically, asimple reduction of current provides insufficient energy to ionize theentire display, resulting in the so called “thermometer effect” whereonly part of the back light is actually illuminated. Another applicationwhere PWM dimming is desirable is in white LEDs. White LEDs suffer anesthetically unacceptable shift in hue or color, as a function ofcurrent. Using pulse-width modulation for dimming white LEDs maintains aconstant current during “on” time, so that a constant color ismaintained over a large dimming range. Switching power supply controller1200 also has input pins for use in temperature compensation: aninternal temperature sensor is included, as well as external pins forreading an external temperature sensor. Temperature compensation is usedin battery-charging to tailor a rate of charge, to respond to unsafeenvironmental conditions, to detect fault conditions and to prevent thedestruction of external batteries or damage due to excessive heatbuild-up. The internal battery charger algorithms accommodate a numberof different chemistries (e.g., lithium ion). Any chemistry can beaccommodated since battery charging algorithms are provided in softwareto be executed in central processing module (SYS) 1205.

[0157] Switching power supply controller 1200 also allows selectionbetween different batteries as its power supply. Central processingmodule (SYS) 1205 can be programmed to use an external battery first,thus preserving its internal battery for emergency situations or whilethe external battery is being changed. It can also automatically chooseto charge the internal battery first, and then external accessorybatteries second. Central processing module (SYS) 1205 computes how muchenergy is available and charge both batteries at the same time or usethem in parallel. Another function provided by a product using thepresent invention is the ability to provide the voltage, current andcoulombmetric data to the outside system. This permits independentdirect control over the voltage regulator functions and intermediatereadings of the amount of energy available in a battery before anindividual threshold. A system encompassing the present invention alsomaintains a charge acceptance history. This is useful in determiningwhether the battery may be fully charged. It's also an early indicatorof battery wear out and provides a basis for limiting overcharge eventswhere the battery may be indefinitely charged because of some sort ofmalfunction.

[0158] In accordance with one aspect of the present invention, theindividual switching waveforms of the product are carefully staggered sothat the amount of energy that is derived from an external power source,for example, a battery, is made as uniform as possible around all of thedifferent outputs that require power. This effectively raises thefrequency of the current required from the external source and mayreduce the peak current demanded from an external source, which reducesthe amount of noise on that external source and also reduces the noiseradiated from the interconnecting wires to the external source and makesthe noise easier to filter. Additionally, a spread spectrum approach isapplied to internal frequencies. This reduces the net energy at a givenfrequency from external switching power supply functions. That is to saythat instead of always operating at a constant frequency, the spreadspectrum feature allows the switching frequency to be varied rapidly andthat frequency modulated using industry standard patterns so that theenergy at any particular frequency is reduced. The spread spectrumfeature effectively reduces noise that would be experienced by anassociated radio either within a product using the present invention,within the end product that this chip is implemented within or otherproducts that are nearby. The frequency of operation can also bedetermined by external sources. In one embodiment, a 32 kilohertzcrystal oscillator generates all the internal clocks and provides a 32kilohertz time based output for use by other elements within the system.According to another feature, the system provides an external clockwhich is guaranteed to be 20 nanoseconds away from the nearest switchingedge. This unique feature allows the external system to conduct samplingsynchronously with the switching power supply functions in the same waythe system synchronously samples to reduce switching noise internally.Normal switching prior art switching power supplies, since they have noknowledge of what duty cycle they're going to provide in any givencycle, have no way to provide this information ahead of time. Since allof the pulse width modulators used in the present invention are digital,this is achieved by another control signal that is scheduled within thearray of control signals that make up all the pulse width modulators.

[0159] Referring to FIG. 12, clock generator macro 1223 (CLKGEN)generates clock signals required by the modules illustrated in FIG. 12.The clock generator module 1223 is illustrated in greater detail in thehigh level block diagram of FIG. 34 which shows the interface signals.The clock generator generates the clocks based on a source clock signalsprovided by digital pulse control module 1201. These source clock pulsesare received by clock generator module 1223 over CST[9:0] output bus1223.2 and the output ports PLOCK and PLLCK from DPC 1201 which areprovided on interfaces 1223.4 and 1223.1, respectively. In the tablebelow, the frequencies of the signals on the CST bus 1223.2 areillustrated.

[0160] Referring to the various interfaces to clock generator 1223, theCST interface from DPC module 1201 is comprised of a 10-bit busindicated by reference character 1223.2 and FIG. 34. The bus isconnected to the output of the GREY counter in DPC 1201 and provides themajority of the source clocks for clock generator 1223. Table 102A showsthe frequency of the signals on each of the bus lines CST[0] to CST[9].TABLE 102A CST Bit Frequency khz CST[0] 134,217.728 CST[1] 67,108.864CST[2] 33,554.432 CST[3] 16,777.216 CST[4] 8,388.608 CST[5] 4,194.304CST[6] 2,097.152 CST[7] 1,048.576 CST[8] 524.288 CST[9] 524.288

[0161] The 2-bit bus PD_OUT[1:0] indicated by reference character 1223.3controls the mode of operation of the generated clock signals. Powermodes of operation are designated as Standard, Low Power and Shut Down.Table 102B below shows the modes as function of the signals on the 2-bitbus. TABLE 102B PD_OUT[1] PD_OUT[0] Mode 0 0 Shut Down 0 1 TBD 1 0 LowPower 1 1 Standard

[0162] The clock signal to analog to digital converter 1206 is providedover line 1223.7 and the frequencies at the various modes are indicatedas set forth below in Table 102C. The Low Power and Standard modefrequencies are derived from the 538,870.921 khz DPLL clock through adivision by 5. TABLE 102C Mode Frequency (khz) Shut Down 0 Low Power107,374.1824 Standard 107,374.1824

[0163] The clock signal to the sample and hold block 1207 is providedover line 1223.9. The frequency which is needed for the various modes ofoperation is shown in Table 102D below. The Standard mode frequency isderived from bit CST[4] bit, and the Low Power mode frequency is derivedfrom a division of the CST[8] bit by 2. TABLE 102D Mode Frequency (khz)Shut Down 0 Low Power 262.144 Standard 8,388.608

[0164] The clock signal to the internal voltage supply 1209 is providedover line 1223.8 and the frequencies needed for the various modes ofoperation are illustrated in Table 102E below. The Standard modefrequency is derived from the CST[4] that, in the Low Power modefrequency is derived by the division of the CST[8] bit by 2. TABLE 102EMode Frequency (khz) Shut Down 0 Low Power 1,048.576 Standard 0

[0165] The clock signals for touch screen interface 1211 are provided bythe QSADC_CLK. The frequencies for the various modes of operations areshown in Table 102F below. The Low Power and Standard mode frequenciesare derived from the CST[8] bit through a division by 2. TABLE 102F ModeFrequency (khz) Shut Down 0 Low Power 262,144 Standard 262,144

[0166] Regulation control module (REG) 1204 is provided clock signalsfor the Standard, Low Power and Shut Down modes by the clock generator1223, and the frequency for each is indicated in Table 102G below. Thefrequencies for the various modes are derived, for example the Standardmode by using CST[0] bit and the low power operating frequency isderived from bit CST[8] through a division by 4. In addition, CLKGEN1223 provides the SHM CLK and SYS CLK clock signals to regulationcontrol module (REG) 1204. TABLE 102G Mode Frequency (khz) Shut Down 0Low Power 131.072 Standard 134,217.728

[0167] Table 102H illustrates the modes and frequencies for those modesfor the clock signal provided to central processing module (SYS) 1205.As illustrated in Table 102H, in the Shut Down mode the frequency is 0.For the Low Power and Standard modes, the frequencies are identical andthey are derived from CST[2]. TABLE 102H Mode Frequency (khz) Shut Down0 Low Power 33,554.432 Standard 33,554.432

[0168] The LED_CLK is a clock used for the LED block which is associatedwith central processing module (SYS) 1205. The frequencies for thevarious modes of operation are indicated in Table 102I below. TheStandard Mode frequency is derived from the CST[8] through a division by2. TABLE 102I Mode Frequency (khz) Shut Down 0 Low Power 0 Standard262.144

[0169] A digital supply voltage of 3.3 V±300 mV is provided to clockgenerator block 1223 via VDD which is connected to the core digitalpower supply. Similarly, VSS is provided over line 1223.6 and is thecore digital ground.

[0170] Turning to FIG. 35, the port table is illustrated showing theport names, whether it is an input or an output, the description as wellas the source and destination of the signals for those ports.

[0171] Referring to FIG. 12, reset circuit 1221 generates the resets forswitching power supply controller 1200. The signals received by thiscircuit and produced by the circuit are indicated within the block. Aswith the other circuits shown in FIG. 12, the arrow adjacent to thesignal name indicates whether the signal is generated by or received byreset circuit 1221.

Section 1.1 Detailed Descriptions of the DPC and Operation, AlternativeImplementations

[0172] Digital Pulse Converter wrapper 1201 can be implemented as acombination of a custom mixed-signal circuit (DPC) and an interfacewrapper of digital glue logic synthesized from a logic circuitdescription expressed in a hardware description language (HDL). In thisimplementation, digital pulse converter wrapper 1201 converts 10-bitdigital values to pulses with edges resolved to about 2 ns. As explainedin further detail below, dual-port memory block with a single write portand a single read port is provided to store 10-bit values that expresspulse start and width control, cycle skipping and bypass circuitrycontrol (for direct output control).

[0173]FIG. 13 is a block diagram showing interface signals of digitalpulse converter wrapper 1201, according to one implementation. As shownin FIG. 13, digital pulse converter wrapper 1201 has five interfaces:(a) timing control interface 1301, (b) regulation control interface1302, (c) power regulation interface 1303, (d) sample and hold controlinterface 1304, and (e) power supply interface 1305.

[0174] Timing control interface 1301 includes 32 KHz, 50% duty cyclereference clock signal 1301 a (FREF), reference clock bypass controlsignal 1301 b (BYPASS), digital phase-locked status signal 1301 c(PLOCK), count time state bus 1301 d (CS[9:0]), and output state bus1301 e (STATE[15:0]), which are used to provide clocks and controlstates for the circuitry external digital pulse converter wrapper 1201.In this implementation, reference clock signal 1301 a (i.e., signalFREF) is a reference clock provided to a digital phase-locked loop(DPLL) in digital pulse converter wrapper 1201 for frequency synthesis,and bypass controls signal 1301 b (i.e., the BYPASS signal) is a testcontrol signal used for bypassing the DPLL. PLOCK is a status signalindicating a phase-locked condition of reference clock signal 1301 a inthe DPLL. Count time state bus 1301 d (i.e., bus CS[9:0]) is a 10-bitclock state bus which provides the clocks and control states tosynchronize the DPC, the interface and other core circuits of switchingpower supply controller 1200. While count time state bus 1301 dcollectively displays the time state of the DPC, individual bits ofcount time state bus 1301 d can be used as 50% duty cycle clocks. Forexample, if a 31.25 KHz reference clock is used, bit CS[9] correspondsto a 256 KHz clock with a 50% duty cycle, bit CS[8] corresponds to a 512KHz clock with a 50% duty cycle. In general CS[n] corresponds to a 50%duty cycle clock with frequency f(n,m)=2^(−(n+m)) f₀, where n ε {0, 1, .. . , 9} and m ε {0, 1, . . . , 6}. Output state bus 1301 e (i.e., busSTATE[15:0]) is a 16-bit state bus which displays the internal state ofswitch control buses 1303a and 1303b (described below) prior to passingthrough the direct control logic used by regulation control interface1303 to force the output signals of switch control bus 1303 a (i.e.,HIGHFET) and switch control bus (i.e., LOWFET) to specific states. Bus1301 e signals when write operations can occur to the DPC core circuit.

[0175] Regulation control interface 1302, which provides access to thedual-port memory in digital pulse converter wrapper 1201, includesmemory write data bus 1302 a (DWI[9:0]), memory address bus 1302 b(ADW[7:0]), memory read data bus 1302 c (DWO[9:0]), write-enable signal1302 d (WE) and read-enable signal 1302 e (RE). Regulation controlinterface 1302 controls the offsets and pulse widths for the variouspulses in power regulation interface 1303.

[0176] Power regulation interface 1303 includes switch control bus 1303a (HIGHFET[6:0]) and switch control bus 1303 b (LOWFET[6:0]). Sample andhold control interface 1304, which controls the sampling and holding ofanalog voltages for digital conversion by the ADC used in the systemcontrol loop, includes a first sample control bus 1304 a (SMPA[6:0]), asecond sample control bus 1304 b (SMPB[6:0]), and an auxiliary controlbus 1304 c (SMPAX[3:0]). The timing for each bit in the sample buses1304 a and 1304 b is associated with each bit of the correspondingswitch bus 1303 a or switch bus 1303 b. Each of sample buses 1304 a and1034 b controls the sampling and holding of analog voltages associatedwith either the HIGHFET or LOWFET control buses for digital conversion.Sampling control bus 1304 c (i.e., auxiliary sample SMPAX[3:0]) controlsthe sampling of other analog signals needed for system monitoring andcontrol.

[0177] Power supply interface 1305 includes digital power reference 1305c (VDD), analog power reference 1305 d (AVD), digital ground reference1305 a (VSS) and analog ground reference 1305 b (AVS). Digital power andground reference signals (i.e., VDD and VSS references) are globalsignals. In this implementation, VDD is the digital high voltage supply(3.3V±10%) connected to the core digital power supply. AVD is the analoghigh voltage supply (3.3V±10%) connected to the core analog powersupply. VSS and AVS are, respectively, the digital ground and analogground references (0V) connected to the core digital ground reference.

Section 1.1.1 First Embodiment of PWM Timing Generator

[0178]FIG. 3 shows a supply management controller of a type inaccordance with this invention. As shown in FIG. 3, a ring oscillatorincludes inverters 301-1 through 301-15 connected in series. In anactual embodiment of this invention, the ring oscillator may include alarger number of series-connected inverters. For example, a thousandinverters can be connected in series, with the result that the dutycycle achieved by the controller of this invention can be almost 100%.However, to simplify explanation, only 15 inverters will be illustratedin this detailed description. The inverters each have inherently a delay“Δ,” which is the elapsed time between the time a signal is applied tothe input lead to the inverter and the time the resulting output signalis obtained on the output lead of each inverter. This time “Δ” is afunction of the voltage applied to the components contained within theinverter. By varying the voltage applied to the inverter's components,the actual delay time A associated with an inverter can be varied. Atypical inverter in CMOS technology will contain a P-channel MOS deviceseries connected with an N-channel MOS device between a voltage sourceand a reference voltage, typically system ground. Should buffers be usedwith an inverter an additional four transistors may be used giving eachinverter six transistors. The delay associated with the transmission ofa signal through the inverter is a function of the voltage applied tothe inverter. The higher the supply voltage applied to the inverter, theslower the transmission of the signal from the input to the output leadand the larger the delay Δ.

[0179] In the structure of FIG. 3 a crystal 302 capable of oscillatingat 32.768 KHz is connected by leads 303 a and 303 b to an invertingamplifier 304. Amplifier 304 provides a voltage across the crystal tocause the crystal to oscillate at 32.768 KHz, thereby causing the outputsignal from inverting amplifier 304 to oscillate at the frequency ofcrystal 302. The output signal of the ring oscillator is divided byeight in divided-by-eight circuit 305 and then sent to phase comparator306, which receives also the output signal from oscillator 302. Thus thecontrol frequency of the ring oscillator is 262.144 KHz, eight times thenormal frequency of crystal 302.

[0180] The normal operating frequency of the ring oscillator isgenerally selected to be approximately the 262 Khz. The phase comparator306 senses the phase difference between the phase of thedivided-by-eight output signal from the ring oscillator and the phase ofthe signal from crystal oscillator 302. Phase comparator 306 providesthis phase difference in an output signal on lead 306 a to Vcc controlcircuit 307 to correct any deviation in the frequency of the ringoscillator's divided-by-eight output signal from the control frequency32.768 Khz associated with crystal oscillator 302. Should the ringoscillator be at too low a frequency, then Vcc control circuit 307 isdriven to provide a higher voltage on lead 307 a to the inverter 301-15,thereby decreasing the delay time associated with this inverter and thusincreasing the oscillating frequency of the ring oscillator.Alternatively, if the operating frequency of the ring oscillator is toohigh, then Vcc control circuit 307 provides a lower output voltage onoutput lead 307 a, thereby increasing the delay time through inverter301-15 and thus lowering the voltage associated with this inverter.

[0181] Phase selector 308 controls the width of a pulse width modulated(PWM) output signal on output lead 310 from exclusive OR gate 309. Eachof the two input leads to exclusive OR gate 309 is coupled by phaseselector 308 to a tap associated with one output lead from an inverter301-i in the ring oscillator. The output leads from the even-numberedinverters 301 are connectable one at a time to input lead 309 a ofexclusive OR gate 309. The output leads from the odd-numbered inverters301 are connectable one at a time to input lead 309 b of exclusive ORgate 309. The particular output leads from inverters 301-1 through301-15 to be connected to input leads 309 a and 309 b of inverter 309are selected depending upon the requirements of the power supply beingdriven by the PWM signal on output lead 310 from exclusive OR gate 309.

[0182] Exclusive OR gate 309 will have a high output whenever its inputsare different. This happens each time a high edge or a low edgepropagates through the ring oscillator past the inverters that theexclusive OR gate is attached to. Since one cycle of the ring oscillatorcontains both a rising edge and a falling edge, the PWM signal observedat output lead 310 of exclusive OR gate 309 will be twice the frequencyof the ring oscillator.

[0183] The normal frequency “f” of the ring oscillator (made-up ofinverters 301-1 through 301-15) is given by the delay time “Δ”associated with each of the inverters. Thus if all inverters have equaldelays, then the normal frequency f=1/(2nΔ) where n is the number ofinverters and Δ is the delay time associated with each inverter. Thusthe frequency is inversely proportional to the number of inverters. Theperiod of the ring oscillator is given by 1/f. Thus if the number ofinverters equals 1,000 and the delay associated with each inverter is10⁻⁹ seconds, then the frequency is 500 Khz and the period is 2microseconds.

[0184] The various pulse widths which the system is capable of achievingare determined by the taps on the output leads of the inverters whichare connected to the input leads 309 a and 309 b of exclusive OR gate309.

Section 1.1.2 Second Embodiment of the PWM Timing Generator

[0185]FIG. 4 shows an alternative embodiment of the invention employingcounters and comparators to generate a pulse width modulated signal. Afive bit counter 41 (although a different number of bits can be used ifdesired) counts from 0 to 31 driven by a 16.7772 MHz signal. Theinstantaneous count from 5 bit counter 41 is sent on 5-bit bus 42 tocomparators 43 a and 43 b, each of which compares the count to areference count stored in it. Digital comparator 43 a will store onecount determined by the signals on phase select bus 44 a and digitalcomparator 43 b will store a second count determined by the signals onphase select bus 44 b. The signals on phase select bus 44 a and phaseselect bus 44 b are determined by external circuitry which measures thevoltage on the load capacitor and the current into the load capacitorand compares the voltage and current to reference values to determinethe extent to which the charge on the load capacitor must bereplenished. This is accomplished by switching power supply controller1200, using in particular sample and hold circuit 1207, analog todigital converter 1206 and regulation control module (REG) 1204. Thesecircuits, as well as their operation and the operation of the system aredescribed in detail below. The output signal from digital comparator 43a toggles a D flip-flop 45 a and the output signal from digitalcomparator 43 b toggles a D flip-flop 45 b. The inverting output signalfrom D flip-flop 45 a is transferred on lead 47 a to the input lead of adelay line 48 a. The delay line has a length determined by bits 4-0 soas to correspond to the time taken to drive the 5-bit counter to theparticular value which causes digital comparator 43 a to toggleflip-flop 45 a. The output signal from the delay line is transferred onlead 49 a to one input lead of exclusive OR gate 49.

[0186] 5-bit counter 41 continues counting after finding a match indigital comparator 43 a until another match is found in digitalcomparator 43 b. The particular value of the count in digital comparator43 b is set by bits 9-5 derived from phase select-red bus 44 b asdescribed below. The match results in input signal being sent fromdigital comparator 43 b to D flip-flop 45 b. D flip-flop 45 b thenproduces an output signal on lead 47 b, which is transmitted to theinput lead of delay line 48 b. Delay line 48 b then produces a highlevel output signal on lead 49 b to exclusive OR gate 49. During thetime that the output signal from delay line 48 a is high and the outputsignal from delay line 48 b is low, a pulse width modulated signal willbe produced by exclusive OR gate 49 on output lead 49 c. When however,the output signals on output leads 49 a and 49 b are the same level,exclusive OR gate 49 will produce a low level output signal on outputlead 49 c. Thus the output signal from exclusive OR gate 49 isphase-modulated in response to the signals on phase select-green andphase select-red buses 44 a and 44 b, respectively.

[0187] Selecting 16.7772 MHz to drive 5-bit counter 41 causes it tocycle through its complete count 524,287½ times per second. In otherwords, the output frequency of the signal on lead 49 c from circuitryFIG. 4 is 262,144 KHz. FIG. 5 illustrates waveforms of a string of13-series connected inverters. The top curve represents the input signalto the first inverter. The second curve represents the output signalfrom the second inverter. The third curve represents the output signalfrom the fourth inverter and the fifth, sixth, seventh and eighth curvesrepresent the output signals from the sixth, eighth, tenth and twelfthinverters, respectively. The bottom curve represents the pulse widthmodulated output signal from the circuit as shown in FIG. 3 or FIG. 4.Note that, in this example, the output signal is controlled by thesignals input to the series-connected inverters and the signal outputfrom the tenth inverter. Note that the output signal is off when thesignal input to the series-connected inverters and the signal outputfrom the tenth inverter are the same amplitude and is on when these twosignals are of complementary amplitudes. In one embodiment, discussedbelow, where the PWM signal drives a main switch of a DC/DC converter,the output current is sampled when the switch is on as shown by thedashed line and the output voltage is sampled when the switch is off asshown by the dashed line at the left hand portion of the curves. Theoutput frequency of the pulse width modulated signal is 524,288 Hz whilethe frequency of change of the signals from the series-connectedinverters is half this frequency over 262,144 Hz.

Section 1.1.3 Discussion of Counter+Comparators Approach—without DelayLines—Optimization Techniques in the Implementation

[0188] Digital Pulse Converter wrapper 1201 may have variousimplementations and include various types of interfaces to perform itsfunctions (e.g., pulse width modulation), as described herein. Forexample, pulse width modulation may be performed utilizing 1) a lowfrequency digital phase locked loop (DPLL) voltage controlled oscillator(VCO) with inverter stages and taps (e.g., as described in reference toFIG. 3), 2) a high frequency DPLL with a counter combined with a digitalcomparator, or 3) a DPLL combined with a content addressable memory(CAM) to generate the required pulse width modulated signals.

[0189]FIG. 36 shows an exemplary pulse width modulation implementation,which includes a pulse width generator (PWG) 2300.4 and a sequencer2302.4, for digital pulse converter 1201. As illustrated herein, thisexemplary pulse width modulation implementation is directed to a highfrequency DPLL with a counter combined with a digital comparator (i.e.,example 2 as listed above), with one DPLL/counter/comparator combinationfor each power supply to be regulated.

[0190] PWG 2300.4 receives a 10-bit trigger (TRG[9:0]) signal and an8-bit tag (TAG[7:0]) signal from sequencer 2302.4, along with areference clock (FREF) and a reset (RST) signal. PWG 2300.4 generates alock (PLOCK) signal, a sequencer clock (SCLK) signal, a pulse widthmodulation (PWM[7:0]) signal, and a clock (CLK[m:n]) signal. Sequencer2302.4 generates the trigger (TRG[9:0]) signal and the tag (TAG[7:0])signal and receives the global reset RST signal and a data (DATA[p:0])signals from a control logic block such as regulation control module(REG) 1204. Sequencer 2302.4 also receives or provides control(CNTL[q:0]) signals.

[0191] The tag signal allows the start and stop times of different PWMsignal outputs to occur at the same trigger value (i.e., time). Thisallows the PWN start and stop times to slide through each other (i.e.,vary independently in time relative to each other) during normaloperation. As an example of a sequence control, the trigger signalvalues (n0, n1, n2, . . . , n15) correspond to the tag signal values(t0, t1, t2, . . . , t15), where 1023≧n15> . . . >n2>n1>n0≧0 (where 1023represents a time duration from 0 to 1023 from a counter). If t1corresponds to the start of the PWM[3] signal and t8 corresponds to thestop of the PWM[3] signal, then the pulse width of the PWM[3] signal isPWM[3]=(n8-n1)τ, where τ≅2 ns.

[0192]FIG. 36A is an exemplary implementation of pulse width generator2300.4 of FIG. 36. FIG. 36A includes a DPLL 2304.4 that generates thelock signal and an output frequency (F_(OUT)) signal that is provided toa divider counter 2308.4 that generates the clock signal. The mostsignificant bit of the clock signal is divided by 16 (by divider 2306.4)to provide a feedback signal for comparison to the reference clock.Divider counter 2308.4 also generates a 10-bit count (CNT[9:0]) signalthat is compared to the trigger signal by a comparator 2310.4, whoseoutput is clocked out to a PWM circuit 2314.4 via a flip flop 2312.4.

[0193] PWM circuit 2314.4 also receives the tag signal and generates thePWM signal and the sequencer clock signal. An exemplary circuitimplementation for PWM circuit 2314.4 is illustrated by a circuit2316.4.

[0194]FIG. 36B is an exemplary implementation of sequencer 2302.4 ofFIG. 36. FIG. 36B includes a series of registers 2330.4 (which areseparately referenced as 2330.4 a through 2330.4 p) and multiplexers2332.4 (which are separately referenced as 2332.4 a through 2332.4 n)that are clocked by the sequencer clock (SCLK) signal and generate thetrigger signal and the tag signal. Registers 2330.4 and multiplexers2332.4 are controlled by a controller 2334.4, which receives the datasignal and receives or provides the control signals. Controller 2334.4operations may be performed by regulation control module (REG) 1204 orby a separate controller, such as a processor or a microcontroller, toprovide the control and data sequencing logic.

[0195]FIG. 36C shows an exemplary feedback control system for a PWMswitching voltage regulator without a dead zone. For example, thefeedback control system monitors a voltage of interest (V_(M)) andcompares it to a target voltage (V_(T)) to generate an estimated PWMstop target (i.e., stop time) for use by controller 2334.4. FIG. 36Cincludes an analog-to-digital converter (ADC) 2340.4, a subtractor2342.4, a summer 2344.4, and a register 2346.4.

[0196] The voltage (V_(M)) is digitized by ADC 2340.4 and subtractedfrom the voltage (V_(T) or digital DV_(T)) by subtractor 2342.4 andsummed with an output of register 2346.4 by summer 2344.4. Register2346.4 provides a PWM stop target (PWM_(ST)) signal.

[0197] If the voltage (V_(T)) is greater than the voltage (V_(M)), thenthe PWM stop target signal is incremented until the voltage (V_(T)) isless than the voltage (V_(M)), which results in the PWM stop target(PWM_(ST)) signal to decrement. Once steady state is achieved, thecontrol loop will continue incrementing and decrementing the PWM stoptarget (PWM_(ST)) signal to minimize the difference between the voltage(V_(T)) and the voltage (V_(M)). This negative feedback control systemrelies on the fact that an increase in the PWM stop target (PWM_(ST))signal will cause an increase in the voltage (V_(M)). The transientresponse of the control loop is small because the change in the PWM stoptarget (PWM_(ST)) signal will be, for example, only one unit (e.g., ±2ns) from cycle to cycle.

[0198]FIG. 36D shows an exemplary feedback control system for a PWMswitching voltage regulator with a dead zone. For example, the feedbackcontrol system monitors a voltage of interest (V_(M)) and compares it toa target voltage (V_(T)) to generate an estimated PWM stop target (i.e.,stop time) for use by controller 2334.4. FIG. 36D includes converter(ADC) 2340.4, subtractor 2342.4, summer 2344.4, register 2346.4,comparators 2348.4, and a logic gate (OR) 2352.4.

[0199] The voltage (V_(M)) is digitized by ADC 2340.4 and subtractedfrom the voltage (V_(T) or digital DV_(T)) by subtractor 2342.4, withthe result compared to a positive and negative dead zone target bycomparators 2348.4 and 2350.4. The output of comparators 2348.4 and2350.4 is provided to logic gate 2352.4, whose output along withcomparator 2350.4 is summed by summer 2344.4 with an output of register2346.4. Register 2346.4 provides a PWM stop target (PWM_(ST)) signal.

[0200] If the difference (i.e., the voltage (V_(T)) minus the voltage(V_(M))) is less than the positive dead zone target and greater than thenegative dead zone target, the PWM stop target (PWM_(ST)) signal remainsconstant. Otherwise, the PWM stop target (PWM_(ST)) signal isincremented or decremented, as required.

Section 1.1.4 Discussion of PLL/RO Using CAM, Optimization Techniques inCAM Implementation

[0201]FIG. 7 shows the output waveforms from the eleventhseries-connected inverters shown in FIG. 6. In FIG. 6 theseries-connected inverters are shown having pass transistors connectedfrom the output of each of the inverters. For the pass transistorsconnecting the output signals from the odd numbered inverters to inputlead 63 a of exclusive OR-gate 63, each pass transistor is driven by asignal labeled as A, B, C, D, E, or F. Similarly, for pass transistorsconnecting the output signals from the even-numbered inverters to leads63 b to exclusive OR gate 63, each pass transistor is driven by a signallabeled G, H, I, J, or K. The pulse width modulated output signal fromexclusive OR gate 63 is transmitted on output lead 63 c to the loadcapacitor of the particular circuit being powered by the structure shownin FIG. 6. The particular combination of pass transistors to be turnedon determines the width of the pulse width modulated signal output onlead 53 c from exclusive OR gate 63. Turning to FIG. 7, one can see thewaveform from the inverters 1 through 11. The waveform from inverter 11is, of course, fed back in FIG. 6 to the input lead of inverter 1.

[0202]FIG. 7 and FIG. 8 show waveforms for the output signals from eachof the inverters 1 through 11 in FIG. 6. FIG. 7 shows the output signalsfor these inverters as taken straight from each inverter. FIG. 8 showsthe output signals from inverters 1, 3, 5, 7, 9 and 11 taken straightfrom the output lead of each inverter while curves 2, 4, 6, 8 and 10show the complement of the output signal taken from inverters 2, 4, 6, 8and 10. FIG. 9 shows the pulse width for the various combinations ofsignals applied to input leads 63 a and 63 b of exclusive OR gate 63,respectively, throughout the pulse width of the pulse on output lead 63c from exclusive OR gate 63 is shown in the columns labeled pulse width.As can be seen from FIG. 9, only one combination of output signals fromthe various inverters is required to yield the five possible differentpulse widths obtainable using the signals directly from the inverters.Thus the pulse widths 10, 8, 6, 4 and 2 are obtained from using on inputlead 63 a of exclusive OR gate 63 the output signal from inverter 1activated by pass transistor A together with one of the output signalsfrom inverters 2, 4, 6, 8 and 10 activated by pass transistors G, H, I,J or K. Thus pulse widths of 10 delays, 8 delays, 6 delays, 4 delays and2 delays are obtained using these combinations. The only othercombination of output signals is that which uses the output signal forinverter 11 together with the output signals from inverters 2, 4, 6, 8and 10, which again yields pulse widths of 2, 4, 6, 8 and 10 delays.

[0203] If output signals from the even-numbered inverters are inverted,then pulse widths of 1, 3, 5, 7, and 9 delays can be obtained bycombining an exclusive OR gate 63 the output signal from inverter 1 withthe output signal from inverters 2, 4, 6, 8 and 10, each inverted.Again, this set of pulse widths represent all possible pulse widthsobtainable using inverted output signals from the even-numberedinverters together with the output signal from any one of theodd-numbered inverters.

[0204] An alternative implementation for performing pulse widthmodulation by digital pulse converter 1201 includes a DPLL combined witha content addressable memory (CAM) to generate the required pulse widthmodulated signals (i.e., example 3 as listed above).

[0205] Digital Pulse Converter (DPC) 1201 is a low power custommixed-signal macro. In general, the input and output signals of DPC 1201are digital, however separate analog power and ground signals areprovided to supply an internal digital phase lock loop (DPLL) circuitused for frequency synthesis.

[0206] DPC 1201 synthesizes a reference clock (32.768 khz) to produce avariety of pulses with pulse widths based on a DPC frame which startswith a count of 0 and ends with a terminal count of 1023, as illustratedin the timing diagram shown in FIG. 37. In one implementation the DPLLgenerates a frame clock of 524.288 KHz, yielding a frame time of 1.907μSec. The minimum pulse width is represented by a count difference of 0(i.e., 0% duty cycle) and the maximum pulse width by a count differenceof 1024 (i.e., 100% duty cycle).

[0207] The rising and falling pulse edges have a minimum resolution of 1count, which corresponds to a real time difference of −1.863 ns. Thepulses are used to control chip I/O output drivers within NFET drivermodule 1202 for external power regulation. The pulses are also used tocontrol chip I/O input drivers within sample and hold module (SHM) 1207,with sample and hold circuits for analog to digital conversion using anon chip analog to digital converter (ADC) found within analog to digitalconverter 1206.

[0208] DPC 1201 also generates other output signals used by other chipcircuitry, for example real time clock states and synchronization pulsesfor regulation control module (REG) 1204, and source clocks for a ClockGeneration and Enable (CKGEN) macro 1223. DPC 1201 generates pulses asshown in FIG. 37, where one DPC frame corresponds to ˜1.907 us in thetiming diagram.

[0209] Each pulse (i.e., a PFET pulse 2410.4, a SFET pulse 2412.4, aSMPA pulse 2414.4, and a SMPB pulse 2416.4 associated respectively witha PFET signal 2402.4, a SFET signal 2404.4, a SMPA signal 2406.4, and aSMPB signal 2408.4) generated by DPC 1201 is represented as a pair of10-bit Grey coded numbers, which are presented to DPC 1201 through theinterface of Regulation control module (REG). The Grey coded numbers aredesignated as Primitive numbers or simply Primitives, with a pair ofPrimitives associated with each pulse.

[0210] The first Primitive number (i.e., a PFTS, a SFTS, a SPAS, and aSPBS in FIG. 37) in each pair indicates the offset of the leading edgeof the pulse from a count of 0 and can be any integer from 0 to 1023.The second Primitive number (i.e., a PFTR, a SFTR, a SPAR, and a SPBR inFIG. 37) in each pair indicates the offset of the trailing edge of thepulse from a count of 0 and can also be any integer from 0 to 1023. Theletter “S” on the end of signal parameters for the first Primitivenumbers (PFTS, SFTS, SPAS, and SPBS) stands for SET and the letter “R”on the end of signal parameters for the second Primitive numbers (PFTR,SFTR, SPAR, and SPBR) stands for RESET.

[0211] PFET pulse 2410.4 and SFET pulse 2412.4, shown along the ordinateof the timing diagram in FIG. 37, control Primary and Secondary NFETdrivers in NFET driver module 1202 and SMPA pulse 2406.4 and SMPB pulse2416.4 control the input sample and hold circuits in SHM 1207. Thepulses shown in the diagram can be represented by 8 independent 10-bitPrimitives.

[0212] The eight independent Primitives are designated as follows: PFTS,PFTR, SFTS, SFTR, SPAS, SPAR, SPBS and SPBR.

[0213] These primitive numbers (i.e., PFTS, PFTR, SFTS, SFTR, SPAS,SPAR, SPBS and SPBR) are stored in a special purpose, dual port contentaddressable memory (CAM) device in DPC 1201 and the notation for thesenumbers are described in detail for port descriptions below. The timingdiagram in FIG. 37 shows the Primitive number set for a single pulsechannel controlled by DPC 1201, however DPC 1201 can provide a number ofindependent pulse channels (e.g., seven independent pulse channels forexternal PWM-switching power conversion and an eighth independentauxiliary pulse channel which can be used for synchronization ofinternal or external circuitry).

[0214] If DPC 1201 provides eight independent pulse channels, then a busnotation for PFET signal 2402.4, SFET signal 2404.4, SMPA signal 2406.4,and SMPB signal 2408.4 may be used to designate these independentchannels as a PFET[7:0] signals 2454.4, a SFET[7:0] signals 2452.4, aSMPA[7:0] signals 2450.4, and a SMPB[7:0] signals 2448.4, respectively,as discussed below in reference to FIG. 37A. PFET[7], SFET[7], SMPA[7]and SMPB[7] refer to the auxiliary pulse channel, and the PFET[6:0]signals 2454.4 and SFET[6:0] signals 2452.4 refer to pulses whichcontrol drivers in NFET driver module 1202 to turn on and off externalpower FETs used for power regulation. The SMPA[6:0] signals 2450.4 andSMPB[6:0] signals 2448.4 refer to pulses which control the input sampleand hold circuits in SHM 1207 for digitizing external analog voltages.It should be noted that the timing diagram shown in FIG. 37 illustratesa break before make switching algorithm between PFET signal 2402 andSFET signal 2404.4 (i.e., between the Primitive number PFTR and thePrimitive number SFTS), which is generally needed for efficient powerregulation.

[0215] DPC 1201 for this implementation has five interfaces tocommunicate with five corresponding portions of switching power supplycontroller 1200 (i.e., IVS 1209, CKGEN 1223, regulation control module(REG) 1204, NFET driver module 1202, and SHM 1207). FIG. 37A illustratesthis exemplary interface implementation for DPC 1201. The interface withIVS 1209 includes the FREF signal 2420.4.

[0216] Additionally, the interface with IVS 1209 includes power andground signals, including a VDD signal 2464.4, an AVD signal 2466.4, aVSS signal 2442.4, and an AVS signal 2444.4. The digital power andground, VDD signal 2464.4 (e.g., 3.3 V) and VSS signal 2442.4,respectively, can be treated as global signals, whereas the analog powerand ground, AVD signal 2466.4 (e.g., 3.3 V) and AVS signal 2444.4,respectively, are generally not treated as global signals.

[0217] FREF signal 2420.4 is a reference clock provided to the DPLL inDPC 1201 and has a frequency and a duty cycle of about 32.768 kHz and50%, respectively. PLOCK signal 2462.4 is a signal which is asserted(i.e., transitions to a logical high or HIGH state) and remains asserted(i.e., remains at a logical high) after the DPLL achieves and remains ina phase lock condition. Otherwise PLOCK is not asserted (i.e., a logicallow or LOW state). AUX signal 2446.4 is an auxiliary signal port that isused for synchronizing circuitry external to switching power supplycontroller 1200.

[0218] The interface with Clock Generator and Enable (CKGEN) 1223includes various signals, including a CST[9:0] signal 2458.4, a PLLCKsignal 2460.4, and a PLOCK signal 2462.4. CST[9:0] signal 2458.4 is a10-bit Grey coded clock state bus which provides the clocks and controlstates to synchronize DPC 1201, regulation control module (REG) 1204,and the CKGEN macro 1223. In a standard operating mode, with SSC signal2424.4 set LOW and FREF signal 2420.4 set to 32.768 kHz, exemplaryfrequencies for the CST[9:0] signals 2458.4 are given in Table 1. PLLCKsignal 2460.4 is the DPLL output clock which has a frequency and a dutycycle of 524.288 kHz and 50% respectively, assuming a referencefrequency for FREF signal 2420.4 of 32.768 kHz. The same frequency forthe last two most significant bits of CST[9:0] signals 2458.4 is anartifact of a 10-bit Grey counter generating these frequencies. The MSB(most significant bit) and NMSB (next most significant bit), (CST[9] andCST[8], respectively, of CST[9:0] signal 2458.4) have a quadrature phaserelationship to each other. TABLE 1 CST Bit Frequency kHz CST[0]134,217.728 CST[1] 67,108.864 CST[2] 33,554.432 CST[3] 16,777.216 CST[4]8,388.608 CST[5] 4,194.304 CST[6] 2,097.152 CST[7] 1,048.576 CST[8]524.288 CST[9] 524.288

[0219] The interface with regulation control module (REG) 1204 includesvarious signals, including PD_OUT[1:0] signals 2426.4, SET[28:0] signals2438.4, RST[28:0] signals 2440.4, ENBL[21:0] signals 2436.4, DWI[19:0]signals 2428.4, DRO[19:0] signals 2456.4, and ADW[4:0] signals 2430.4,which are input buses, and the CST[9:0] signals 2458.4, which is anoutput bus. Additionally, the interface includes an input signal WE2432.4, an input signal RE 2434.4, and an output signal PLOCK 2462.4.

[0220] The interface with the regulation control module (REG) 1204 isused to generate the various pulses, such as PFET pulse 2410.4 and SFETpulse 2412.4. The DWI[19:0] signals 2428.4, ADW[4:0] signals 2430.4,DRO[19:0] signals 2456.4, and input signal WE 2432.4 and input signal RE2434.4 transfer data and control the read/write ports of the dual portCAM, discussed in further detail herein. The read port for the CAM iswithin DPC 1201.

[0221] More specifically, the PD_OUT[1:0] signals 2426.4 are a 2-bit buswhich controls the mode of operation for DPC 1201. The modes ofoperation are designated as Standard mode, Low Power mode, and Shut Downmode, as summarized in Table 2.

[0222] When PD_OUT[1:0] signals 2426.4 are asserting the Shut Down mode,the DPLL is powered down, the CAM is in standby mode, and the rest ofthe digital blocks in DPC 1201 are in low power states. When PD_OUT[1:0]signals 2426.4 are asserting the Low Power mode, the DPLL is powered upand phase locked at its normal operating frequency (536,870.912 kHz),the DPLL output is divided by 16 to produce the LSB of CST[9:0] signal2458.4 (i.e., the frequency of the CST LSB is 33,554.432 kHz), the CAMis in standby mode, and the remaining blocks of DPC 1201 are in lowpower states. When PD_OUT[1:0] signals 2426.4 are asserting the Standardmode, the DPLL is operating normally, the DPLL output is divided by 4 toproduce the LSB of CST[9:0] signals 2458.4 (i.e., the frequency of theCST LSB is 134,217.728 kHz), the CAM is powered up and operatingnormally and the rest of the DPC blocks are also powered up and areoperating normally. TABLE 2 Exemplary Modes PD OUT[1] PD OUT[0] MODE 0 0Shut Down 0 1 TBD/Spare 1 0 Low Power 1 1 Standard

[0223] The SET[31:0] signals 2438.4 are a 32-bit control bus which isused to independently set each output bit of DPC 1201. For example, whenSET[0] of the SET[31:0] signals 2438.4 is HIGH, SMPA[0] of the SMPA[7:0]signals 2450.4 is set HIGH, and when SET[1] of the SET[31:0] signals2438.4 is HIGH, PFET[0] of the PFET[7:0] signals 2454.4 is set HIGH.Table 3 illustrates exemplary associations between SET[31:0] signal2438.4, the Primitive numbers, and output signals from DPC 1201. TABLE 3Set Bits Primitive Numbers DPC Macro Outputs SET[0]-SET[3] SPAS[0],PFTS[0], SPBS[0], SFTS[0] SMPA[0], PFET[0], SMPB[0], SFET [0]SET[4]-SET[7] SPAS[1], PFTS[1], SPBS[1], SFTS[1] SMPA[1], PFET[1],SMPB[1], SFET [1] SET[8]-SET[11] SPAS[2], PFTS[2], SPBS[2], SFTS[2]SMPA[2], PFET[2], SMPB[2], SFET [2] SET[12]-SET[15] SPAS[3], PFTS[3],SPBS[3], SFTS[3] SMPA[3], PFET[3], SMPB[3], SFET [3] SET[16]-SET[19]SPAS[4], PFTS[4], SPBS[4], SFTS[4] SMPA[4], PFET[4], SMPB[4], SFET [4]SET[20]-SET[23] SPAS[5], PFTS[5], SPBS[5], SFTS[5] SMPA[5], PFET[5],SMPB[5], SFET [5] SET[24]-SET[27] SPAS[6], PFTS[6], SPBS[6], SFTS[6]SMPA[6], PFET[6], SMPB[6], SFET [6] SET[28]-SET[31] SPAS[7], PFTS[7],SPBS[7], SFTS[7] SMPA[7], PFET[7], SMPB[7], SFET [7]

[0224] The RST[31:0] signals 2440.4 are a 32-bit control bus which isused to independently reset each output bit of DPC 1201. For example,when RST[0] of the RST[31:0] signals 2440.4 is HIGH, the SMPA[0] outputof the SMPA[7:0] signals 2450.4 is reset LOW, and when RST[1] of theRST[31:0] signals 2440.4 is HIGH, the PFET[0] output of the PFET [6:0]signals 2454.4 is reset LOW. Table 4 illustrates exemplary associationsbetween RST[31:0] signal 2440.4, the Primitive numbers, and outputsignals from DPC 1201. TABLE 4 Reset Bits Primitive Numbers DPC MacroOutputs RST[0]-RST[3] SPAR[0], PFTR[0], SPBR[0], SFTR SMPA[0], PFET[0],SMPB[0], SFET[0] [0] RST[4]-RST[7] SPAR[1], PFTR[1], SPBR[1], SFTRSMPA[1], PFET[1], SMPB[1], SFET[1] [1] RST[8]-RST[11] SPAR[2], PFTR[2],SPBR[2], SFTR SMPA[2], PFET[2], SMPB[2], SFET[2] [2] RST[12]-RST[15]SPAR[3], PFTR[3], SPBR[3], SFTR SMPA[3], PFET[3], SMPB[3], SFET[3] [3]RST[16]-RST[19] SPAR[4], PFTR[4], SPBR[4], SFTR SMPA[4], PFET[4],SMPB[4], SFET[4] [4] RST[20]-RST[23] SPAR[5], PFTR[5], SPBR[5], SFTRSMPA[5], PFET[5], SMPB[5], SFET[5] [5] RST[24]-RST[27] SPAR[6], PFTR[6],SPBR[6], SFTR SMPA[6], PFET[6], SMPB[6], SFET[6] [6] RST[28]-RST[31]SPAR[7], PFTR[7], SPBR[7], SFTR SMPA[7], PFET[7], SMPB[7], SFET[7] [7]

[0225] The ENBL[23:0] signals 2436.4 are a 24-bit CAM enable bus used toindependently enable the CAM match ports. The ENBL[3n] bits ofENBL[23:0] signal 2436.4 enable the SMPA[n] bits of the SMPA[7:0]signals 2450.4 and the SMPB[n] bits of the SMPB[7:0] signals 2448.4 forCAM match outputs, where n ε {0, 1, 2, . . . , 7}. The ENBL[3n+1] bitsof the ENBL[23:0] signals 2436.4 enable the PFET[n] bits of thePFET[7:0] signals 2454.4 for the CAM match outputs and the ENBL[3n+2]bits of the ENBL[23:0] signals 2436.4 enable the SFET[n] bits of theSFET[7:0] signals 2452.4 for the CAM match outputs, where n ε {0, 1, 2,. . . , 7}. The CAM ENBL bus (i.e., the ENBL[23:0] signals 2436.4) andoutput correspondence for an exemplary implementation is given in Table5. TABLE 5 ENBL Bus Bits DPC Macro Outputs ENBL[0] SMPA[0], SMPB[0]ENBL[1] PFET[0] ENBL[2] SFET[0] ENBL[3] SMPA[1], SMPB[1] ENBL[4] PFET[1]ENBL[5] SFET[1] ENBL[6] SMPA[2], SMPB[2] ENBL[7] PFET[2] ENBL[8] SFET[2]ENBL[9] SMPA[3], SMPB[3] ENBL[10] PFET[3] ENBL[11] SFET[3] ENBL[12]SMPA[4], SMPB[4] ENBL[13] PFET[4] ENBL[14] SFET[4] ENBL[15] SMPA[5],SMPB[5] ENBL[16] PFET[5] ENBL[17] SFET[5] ENBL[18] SMPA[6], SMPB[6]ENBL[19] PFET[6] ENBL[20] SFET[6] ENBL[21] SMPA[7], SMPB[7] ENBL[22]PFET[7] ENBL[23] SFET[7]

[0226] The ENBL bits of the ENBL[23:0] signals 2436.4 are active HIGH.To enable specific CAM match ports, the corresponding enable bit is setHIGH. The ENBL[23:0] signals 2436.4 affects only the read port of theCAM and the Primitive numbers can be read from and written to the CAMthrough the read/write port, as described in further detail below. Thisfeature allows the CAM to be safely updated without causing aninadvertent match during a CAM update. In addition, the ENBL[23:0]signals 2436.4 allow the capability for pulse skipping during the normaloperation of the CAM.

[0227] The DWI[19:0] signals 2428.4 are a 20-bit write data bus for theread/write CAM port and it is used for writing Grey coded words to theCAM. The DWI[19:0] bus 2428.4 writes to the CAM are controlled by theADW address bus (i.e., the ADW[4:0] signals 2430.4) and the WE signal2432.4. The DWI[9:0] bits of DWI[19:0] signal 2428.4 are allocated forthe bank zero of the CAM and the DWI[19:10] bits of DWI[19:0] signal2428.4 are allocated for bank one of the CAM.

[0228] The ADW[4:0] signals 2430.4 are a 5-bit address bus used toaddress a single (20-bit) word in the CAM for reading or writing. Forease of implementation and in accordance with one embodiment, the CAM issplit into two banks, as described in Table 6. The ADW[4:0] signals2430.4 simultaneously addresses one 10-bit word out of 22 words in eachCAM bank. For example, ADW[0] of the ADW[4:0] signals 2430.4 correspondsto the Primitive SPBS[0] in the CAM bank zero and the Primitive SPBR[0]in the CAM bank one. TABLE 6 Read/Write CAM Bank Zero CAM Bank One PortADW Primitive Numbers Primitive Numbers ADW[0] SPBS[0] SPBR[0] ADW[1]PFTS[0] PFTR[0] ADW[2] SFTS[0] SFTR[0] ADW[3] SPAS[0] SPAR[0] ADW[4]SPBS[1] SPBR[1] ADW[5] PFTS[1] PFTR[1] ADW[6] SFTS[1] SFTR[1] ADW[7]SPAS[1] SPAR[1] ADW[8] SPBS[2] SPBR[2] ADW[9] PFTS[2] PFTR[2] ADW[10]SFTS[2] SFTR[2] ADW[11] SPAS[2] SPAR[2] ADW[12] SPBS[3] SPBR[3] ADW[13]PFTS[3] PFTR[3] ADW[14] SFTS[3] SFTR[3] ADW[15] SPAS[3] SPAR[3] ADW[16]SPBS[4] SPBR[4] ADW[17] PFTS[4] PFTR[4] ADW[18] SFTS[4] SFTR[4] ADW[19]SPAS[4] SPAR[4] ADW[20] SPBS[5] SPBR[5] ADW[21] PFTS[5] PFTR[5] ADW[22]SFTS[5] SFTR[5] ADW[23] SPAS[5] SPAR[5] ADW[24] SPBS[6] SPBR[6] ADW[25]PFTS[6] PFTR[6] ADW[26] SFTS[6] SFTR[6] ADW[27] SPAS[6] SPAR[6] ADW[28]SPBS[7] SPBR[7] ADW[29] PFTS[7] PFTR[7] ADW[30] SFTS[7] SFTR[7] ADW[31]SPAS[7] SPAR[7]

[0229] The DRO[19:0] signals 2456.4 are a 20-bit read data bus for theread/write CAM port and it is used for reading Grey coded words from theCAM. The DRO[19:0] bus 2456.4 reads from the(CAM are controlled by theADW address bus (i.e., the ADW[4:0] signals 2430.4) and the RE signal2434.4. The DRO[9:0] bits of DRO[19:0] signal 2456.4 are allocated forthe bank zero of the CAM and the DRO[19:10] bits of DRO[19:0] signal2456.4 are allocated for bank one of the CAM.

[0230] The PFET[6:0] signals 2454.4 are a 7-bit bus which provides theprimary power FET pulses (i.e., pulses, such as PFET pulse 2410.4) toNFET driver module 1202. The SFET[6:0] signals 2452.4 are a 7-bit buswhich provides the secondary power FET pulses (i.e., pulses, such asSFET pulse 2412.4) to NFET driver module 1202.

[0231] The WE signal 2432.4 is the write enable control signal for theread/write CAM port. When WE signal 2432.4 toggles HIGH, a 10-bit wordis written to each bank of the CAM at the address specified by theADW[4:0] signals 2430.4. The RE signal 2434.4 is the read enable controlsignal for the read/write CAM port. When the RE signal 2434.4 togglesHIGH, a 10-bit word is read from each bank of the CAM at the addressspecified by the ADW[4:0] signals 2430.4.

[0232] The interface for NFET driver module 1202 includes varioussignals, including the PFET[6:0] signals 2454.4 and SFET[6:0] signals2452.4. As discussed above, a single PFET (primary FET) and SFET(secondary FET) pulse channel is shown in the above timing diagram (FIG.37).

[0233] The interface for SHM 1207 includes various signals, includingthe SMPA[6:0] signals 2450.4 and the SMPB[6:0] signals 2448.4. Thisinterface is used to control the sampling and holding of analog voltagesfor digital conversion by analog to digital converter 1206. As describedabove in accordance with one embodiment, the sample pulses SMPA (e.g.,SMPA pulse 2414.4) and SMPB (e.g., SMPB pulse 2416.4) are independentfrom the PFET (Primary FET) and SFET (Secondary FET) pulses. Either ofthe SMPA[6:0] signals 2450.4 or the SMPB[6:0] signals 2448.4 can be usedto control the sampling (and holding) of analog voltages in SHM 1207 foranalog to digital converter 1206. The remaining signals shown in FIG.37A and described in Table 8 include a bypass signal 2422.4 and the SSCsignal 2424.4. Bypass signal 2422.4 is a test control signal used forbypassing the DPLL. When bypass signal 2422.4 is held HIGH, FREF signal2420.4 bypasses the DPLL, but when bypass signal 2422.4 is held LOW,FREF signal 2420.4 is used for frequency synthesis. SSC signal 2424.4 isa control signal that activates spread spectrum clocking. Spreadspectrum clocking is activated when SSC signal 2424.4 is HIGH; otherwisespread spectrum clocking is disabled. The spread spectrum clockingscheme implemented in DPC 1201 can be either up or down frequencyspreading where the DPC frame frequency (e.g., 524.288 kHz withoutspread spectrum clocking) deviates from its fundamental frequency byapproximately 0.5% with a modulation period of approximately 22 us.TABLE 8 Descriptive Summary of Exemplary Interface Signals Port NameType Description Source Destination FREF Input 32.768 khz ReferenceClock IVS 1209 BYPASS Input Reference Clock Bypass Control REG 1204 SSCInput Spread Spectrum Clock Control REG 1204 PLOCK Output DPLL Lock,Active HIGH CKGEN 1223 PD_OUT[1:0] Input Power Management Control BusREG 1204 PLLCK Output DPLL Output Clock CKGEN 1223 CST[9:0] Output CountTime State Bus CKGEN 1223 REG 1204 ENBL [21:0] Input CAM Section EnableBus REG 1204 DWI[19:0] Input CAM Read/Write Port Data Bus REG 1204 ADW[4:0] Input CAM Read/Write Port Address Bus REG 1204 WE Input CAMRead/Write Port Write Enable REG 1204 RE Input CAM Read/Write Port ReadEnable REG 1204 DRO[19:0] Output CAM Read/Write Port Data Bus REG 1204SET[28:0] Input Pulse Set Bus REG 1204 RST[28:0] Input Pulse Reset BusREG 1204 PFET[6:0] Output Primary FET Control Bus NFET 1202 SFET[6:0]Output Secondary FET Control Bus NFET 1202 SMPA[6:0] Output Sample AControl Bus SHM 1207 SMPB[6:0] Output Sample B Control Bus SHM 1207 AUXOutput Auxiliary Pulse Control Port IVS 1209 VDD Power Digital Power IVS1209 AVD Power Analog Power IVS 1209 VSS Power Digital Ground IVS 1209AVS Power Analog Ground IVS 1209

[0234]FIG. 37B illustrates one circuit implementation for DPC 1201 andincludes a DPLL 2480.4, a spreader divider 2482.4, a Grey counter2484.4, and a CAM module 2486.4. CAM module 2486.4 includes a modifiedCAM for generating PFET[6:0] signal 2454.4, SFET[6:0] signal 2452.4,SMPA[6:0] signal 2450.4, SMPB[6:0] signal 2448.4, and AUX signal 2446.4.FIG. 37C illustrates one exemplary implementation for CAM module 2486.4.

[0235] CAM module 2486.4 stores, for example, 64 words (i.e.,Primitives, which were discussed above), with 10-bits per word and withan address read port 2502.4 (labeled ADR[63:0]) of CAM module 2486.4 notencoded. Address read port 2502.4 provides 64 address signals,referenced collectively as ADR[63:0] signals 2508.4. The even ADR bits(ADR[0], ADR[2], . . . , ADR[62]) of ADR[63:0] signals 2508.4 areassociated with CAM bank zero and the odd ADR bits (ADR[1], ADR[3], . .. , ADR[63]) of ADR[63:0] signals 2508.4 are associated with the CAMbank one, as previously discussed (e.g., in reference to ADW[4:0] signal2430.4). ADR[63:0] signals 2508.4 are connected to 32 RS latches, whichare represented by an RS latch 2504.4 (FIG. 37C), through control logic2506.4, shown in a representative fashion in FIG. 37C. A more detailedexemplary implementation for control logic 2506.4 and RS latch 2504.4,associated with a single pulse channel at the output of CAM module2486.4, is shown in FIG. 37D and discussed below.

[0236] DPLL 2480.4 (FIG. 37B) is shown coupled to Grey counter 2484.4(e.g., a free running 10-bit Grey Counter), with spreader divider 2482.4situated between DPLL 2480.4 and Grey counter 2484.4. When SSC signal2424.4 is enabled, spreader divider 2482.4 produces spread spectrumclocking, as described above, by employing a uniform pulse swallowingtechnique which varies in frequency. Spread spectrum mode of operationis described below.

[0237] Additionally, spreader divider 2482.4 provides the variabledivide ratio for toggling between the standard and low power modes,described above for PD_OUT[1:0] signal 2426.4. The extra divisionprovided by spreader divider 2482.4 reduces the current drawn by Greycounter 2484.4 in the low power mode. For example, as compared to abinary counter, Grey counter 2484.4 produces glitch free read operationsfor CAM module 2486.4.

[0238] An example of operation for the implementation shown in FIG. 37Bfor DPC 1201 starts with DPLL 2480.4, which increments Grey counter2484.4 (i.e., through spreader divider 2482.4) to produce the read data,identified by a DRI signal 2488.4, for CAM Module 2486.4. If the readdata of DRI signal 2488.4 generates a CAM match in CAM Module 2486.4,one or more of the CAM output read address lines (i.e., ADR[63:0]signals 2508.4) of CAM Module 2486.4 becomes active, which sets orresets one or more of the 32 RS latches (i.e., RS latch 2504.4) toproduce the output pulses on the PFET[7:0] signals 2454.4, SFET[7:0]signals 2452.4, SMPA[7:0] signals 2450.4 and SMPB[7:0] signals The 32 RSlatches (represented by RS latch 2504.4) are organized into eight pulsechannels. The 4 pulses within a pulse channel are completely independentas described earlier And the eight independent Primitive numbers (oneset of eight numbers for each pulse channel) are Grey coded and writtento specific address locations in the CAM of CAM module 2486.4 regulationcontrol module (REG) 1204. The address locations for the Primitivenumbers are given above in reference to ADW[4:0] signal 2430.4.

[0239] CAM Module's 2486.4 logic that is associated with one pulsechannel (e.g., given by a PFET[n] signal 2512.4, an SFET[n] signal2516.4, an SMPA[n] signal 2510.4, and an SMPB[n] signal 2514.4, where nE {0, 1, 2, . . . , 7}) is shown in detail in FIG. 37D. Eightindependent CAM ADR lines (e.g., ADR[8n], ADR[8n+1], ADR[8n+2],ADR[8n+3], ADR[8n+4], ADR[8n+5], ADR[8n+6] and ADR[8n+7]) from theADR[63:0] signals 2508.4 are shown controlling four RS latches(separately referenced as RS latches 2504.4(1) through 2504.4(4)) of RSlatch 2504.4.

[0240] The control circuitry for the ENBL[23:0] signals 2436.4, whichare separately referenced as enable control logic 2506.4(1) of controllogic 2506.4, is also shown in detail in FIG. 37D. The ENBL[3n+1]signals and ENBL[3n+2] signals, of the ENBL[23:0] signals 2436.4,control RS latches 2504.4(2) and 2504.4(4) for the PFET[n] signals2512.4 and SFET[n] signals 2516.4, respectively, and the ENBL[3n]signals of the ENBL[23:0] signals 2436.4 controls RS latches 2504.4(1)and 2504.4(3) for the SMPA[n] signals 2510.4 and SMPB[n] signals 2514.4,respectively. Table 5, discussed above, provides additional detailsregarding the ENBL[23:0] signals 2436.4.

[0241] The control circuitry for the SET[31:0] signals 2438.4 and theRST[31:0] signals 2440.4, which are separately referenced as set/resetcontrol logic 2506.4(2) of control logic 2506.4, is also shown in detailin FIG. 37D. The SET[31:0] signals 2438.4 and RST[31:0] signals 2440.4allow direct control of RS latch 2504.4 (e.g., RS latches 2504.4(1)through 2504.4(4)) at the output of CAM Module 2486.4). In the low powermode, this interface is used in conjunction with the ENBL[23:0] signals2436.4 by logic in regulation control module (REG) 1204 to generate theADC samples and power regulation pulses needed for operation in thismode. Using these control signals, regulation control module (REG) 1204can take direct control of RS latch 2504.4 to avoid hazard conditions(e.g., preventing the set (S) and reset (R) inputs to each latch frombeing active simultaneously).

[0242] As shown in FIG. 37C, a CAM 2494.4 is a dual-port memory devicewith one read/write port 2496.4 (associated with the DWI[19:0] signals2428.4, ADW[4:0] signals 2430.4, WE signal 2432.4, RE signal 2434.4, andDRO[19:0] signals 2456.4) and one read port 2498.4 (associated with theDRI signals 2488.4 and ADR[63:0] signals 2508.4). The same Primitivenumber can be written to two or more address locations in CAM 2494.4,which will cause multiple matches on the ADR[63:0] signals 2508.4 (i.e.,the CAM read address lines) when the matching data is presented to readport 2498.4 (through the DRI signals 2488.4) of CAM 2494.4 by GreyCounter 2484.4. The multiple matches allow two or more output edges tocoincide.

[0243] Regulation control module (REG) 1204 synchronizes the writes toCAM 2494.4 to avoid the generation of inadvertent glitches on thevarious pulse channels. When key independent pulse edges (i.e., masteredges) change from one DPC frame of DPC 1201 to the next, regulationcontrol module (REG) 1204 recomputes the dependent pulse edges (i.e.,slave edges) and updates CAM 2494.4 accordingly. The master edgescorrespond to the Primitives PFTS[n], PFTR[n], SFTS[n], and SFTR[n],where n ε {0, 1, . . . , 7}. All other edges are either slave edges orauxiliary edges.

[0244] If a master edge is moved from its position (Grey coded count) inthe current DPC frame of DPC 1201 to a different position in the nextframe, the slave edges related to the specific master edge arere-computed and written to CAM 2494.4 by regulation control module (REG)1204 for use in the next frame. Regulation control module (REG) 1204provides the computations, Grey coding, and CAM write coordinationrequired to perform these tasks efficiently and without hazards.

[0245] The information necessary to compute the slave edges from themaster edge information is contained within regulation control module(REG) 1204, and this information does not generally change from one DPCframe of DPC 1201 to the next. For example, the slave edge informationnecessary to calculate the Primitive data SPAS and SPBS edges for eachchannel can be provided as a single 10-bit binary constant (or pulsewidth), which is used by regulation control module (REG) 1204 to computeand Grey encode a new Primitive SPAS value if a Primitive PFTS valuechanges or (more likely) to compute and Grey encode a new Primitive SPBSvalue if a given Primitive PFTR value changes.

[0246] The master edge information provided by regulation control module(REG) 1204 can change from one DPC frame of DPC 1201 to the next.Regulation control module (REG) 1204 provides this information as pairsof 10-bit Grey coded numbers comprised of two offsets from a DPC 1201frame initial count of zero. One offset corresponds to the SET input ofone of the RS latches (i.e., RS latch 2504.4) at the output of CAMmodule 2486.4 and the other offset corresponds to the RESET input of theRS latch.

[0247] As mentioned above, read port 2498.4 of CAM 2494.4 (associatedwith DRI signal 2488.4) is buried within DPC 1201, as illustrated inFIG. 37B and FIG. 37C. The ENBL[23:0] signals 2436.4 affects only theread port of CAM 2494.4 and is used for the multiple functions describedabove. If a specific ENBL bus bit of the ENBL[23:0] signals 2436.4 isheld LOW, for example ENBL[0] bit, the read address sectioncorresponding to the ENBL[0] bit is disabled and any data matchoccurring in the corresponding disabled section (e.g., the PrimitivesSPAS[0], SPAR[0], SPBS[0] and SPBR[0]) will not produce a match.However, if the same data occurs in another read address section of CAM2494.4, which is not disabled, the match will occur.

[0248] Because the ENBL[23:0] signals 2436.4 only affects the read portof CAM 2494.4, read/write port 2496.4 is not affected. Therefore, readsand writes to CAM 2494.4 through read/write port 2496.4 can take placeunimpeded. This capability can be used in conjunction with the PFET[7:0]signals 2454.4 or SFET[7:0] signals 2452.4 to safely update thePrimitive numbers in CAM 2494.4 and avoid the inadvertent generation ofpulse glitches. One possible update sequence is shown in the timingdiagram of FIG. 37E for updating the Primitive SFTR[0] in CAM 2494.4.

[0249] The Primitive SFTR[0] update to CAM 2494.4 starts with the risingedge of an SFET[0] bit of the SFET[7:0] signals 2452.4. At the risingedge of the SFET[0] bit, the SFTS[0] Primitive match has alreadyoccurred. Regulation control module (REG) 1204 detects the rising edgeof the SFET[0] bit and disables the required CAM section of CAM 2494.4one regulation control module (REG) 1204 clock cycle later by setting anENBL[2] signal LOW. Note that this does not present a problem for aPFET[0] pulse of the PFET[7:0] signals 2454.4, because the rising andfalling edges of that pulse have already occurred.

[0250] After the CAM section of CAM 2494.4 is disabled, regulationcontrol module (REG) 1204 enables a CAM write by toggling WE signal2432.4 HIGH. Because the ADW[4:0] signals 2430.4 (i.e., the read/writeaddress port ADW) has been set to address location 2, which correspondsto the Primitive SFTR[0] as shown in Table 6, the new Primitive forSFTR[0] is written to the CAM address location 2 of CAM 2494.4.Regulation control module (REG) 1204 then re-activates the section bysetting the ENBL[2] bit HIGH and the new falling edge of the SFET[0]pulse of the SFET[7:0] signals 2452.4 occurs at the new SFTR[0]Primitive value when the CAM match occurs as indicated by the fallingedge of the SFET[0] pulse.

[0251] Changing some Primitives has more of an effect on otherPrimitives than the example given in reference to FIG. 37E. Because ofthe dependencies discussed herein, if the Primitive PFTR is changed, thePrimitives SPBS, SFTS, and SFTR may need to be recomputed, Grey coded,and updated to CAM 2494.4 by regulation control module (REG) 1204. Asanother example, if the Primitive PFTS is changed all of the PrimitivesSPAS, SPBS, PFTR, SFTS, and SFTR may need to be recomputed, Grey coded,and updated to CAM 2494.4 by regulation control module (REG) 1204.

[0252] Because the worst case write cycle time for CAM 2494.4 is, forexample, 7.5 ns, the updates described in the previous sentence can becompleted in 22.5 ns (i.e., 3 times 7.5 ns). To update the entire 64words in CAM 2494.4 would take approximately 240 ns. In FIG. 37, as anexample, a break before make switching algorithm for PFET signal 2402.4and SFET signal 2404.4 was presented. If the break time between PFETsignal 2402.4 and SFET signal 2404.4 were always greater than 30 ns, allof the Primitives (eight numbers) necessary to update a pulse channelcan be written to CAM 2494.4 during this period.

Section 1.1.5 Discussion of Combinations and Permutations of PLL/RO, DLLand Counters for Optimization of Standby Power and Die Size

[0253]FIG. 38 shows a circuit 2600.4, which is an exemplaryimplementation for Grey counter 2484.4 (FIG. 37B). Circuit 2600.4represents a 10-bit Grey counter, but could be implemented as any numberof bits based upon the techniques discussed herein. Furthermore, circuit2600.4 can be implemented as a low power circuit utilizing circuittechniques discussed below (e.g., in reference to FIG. 38B through FIG.38F).

[0254] Circuit 2600.4 includes a number of flip flops 2602.4, which areseparately referenced as flip flop 2602.4(1) through 2602.4(10), alongwith a number of AND gates 2604.4 and a number of exclusive OR (XOR)gates 2606.4. Circuit 2600.4 generates a 10-bit Grey count (i.e., bitsC0 through C9 in FIG. 38) that is provided to CAM module 2486.4 (FIG.37B).

[0255]FIG. 38A shows a circuit 2610.4, which is another exemplaryimplementation for Grey counter 2484.4. Circuit 2610.4 is similar toCircuit 2600.4, but utilizes NAND gates 2612.4 and NOR gates 2614.4rather than AND gates 2604.4. As shown in FIG. 38 and FIG. 38A, flipflop 2602.4(1) receives a clock (CLK) signal 2603.4 while flip flops2602.4(2) through 2602.4(10) receive a clock signal (CLK bar) 2605.4,which is the complement of clock signal 2603.4. Circuits 2600.4 and2610.4 may be implemented using low power circuit techniques discussedin the following figures.

[0256]FIG. 38B and FIG. 38C illustrate circuit implementations that mayrequire less power than conventional flip flop circuits by utilizingfewer circuit elements. FIG. 38B shows an exemplary implementation forflip flop 2602.4(1) of FIG. 38 or FIG. 38A. FIG. 38B includestransistors 2620.4 and 2624.4 (i.e., a p-type and an n-type transistor,respectively) along with inverters 2622.4, 2626.4, and 2628.4.Transistor 2620.4 receives a D input signal 2630.4 and transistors2620.4 and 2624.4 receive a clock (CLK) signal 2632.4, with inverters2626.4 and 2628.4 providing a Q signal 2634.4 and a QN (Q NOT or Q bar)signal 2636.4, respectively.

[0257] In a similar fashion, FIG. 38C shows an exemplary implementationfor flip flops 2602.4(2) through 2602.4(10) of FIG. 38 or FIG. 38A. FIG.38C includes transistors 2640.4 and 2642.4 (i.e., an n-type and a p-typetransistor, respectively) along with inverters 2644.4, 2646.4, and2648.4. Transistor 2640.4 receives a D input signal 2650.4 andtransistors 2640.4 and 2642.4 receive a clock (CLK bar) signal 2652.4,with inverters 2646.4 and 2648.4 providing a Q signal 2654.4 and a QN (QNOT) signal 2656.4, respectively.

[0258]FIG. 38D shows an exemplary circuit implementation for an XORlogic gate (e.g., XOR gate 2606.4 of FIG. 38 and FIG. 38A or an XOR gate2717.4 as shown in FIG. 38D), which requires less power than aconventional XOR gate. FIG. 38D includes inverters 2700.4 and 2702.4 andtransistors 2704.4 and 2706.4. An input signal (A) 2708.4 and an inputsignal (B) 2710.4 are provided, as shown, to transistors 2704.4 and2706.4, respectively, with inverter 2702.4 providing an output signal(Z) 2712.4 in accordance with the equation

Z=A{overscore (B)}+{overscore (A)}B.

[0259] Likewise, FIG. 38E shows an exemplary circuit implementation foran exclusive NOR (XNOR) logic gate 2720.4, which may require less powerthan a conventional XNOR gate. FIG. 38E includes inverters 2722.4 and2724.4 and transistors 2726.4 and 2728.4. An input signal (A) 2730.4 andan input signal (B) 2732.4 are provided, as shown, to transistors 2726.4and 2728.4, respectively, with inverter 2724.4 providing an outputsignal (Z) 2734.4 in accordance with the equation

[0260] Z={overscore (A)}{overscore (B)}{overscore (+)}{overscore(A)}{overscore (B)}.

[0261] Additionally, FIG. 38F shows an exemplary circuit implementationfor an inverting multiplexer 2740.4, which includes transistors 2742.4and 2744.4 and an inverter 2746.4. Inverting multiplexer 2740.4 receivesinput signals (A) 2748.4, (B) 2750.4, and (C) 2752.4 and provides anoutput signal (Z) 2754.4, in accordance with the equation

[0262] Z={overscore (CB+)}{overscore (C)}{overscore (+A)}.

[0263]FIG. 38G shows an exemplary circuit implementation for a binary toGrey conversion (BGC) 2770.4 and a Grey to binary conversion (GBC)2780.4. BGC 2770.4 shows an exemplary 4-bit conversion from binary toGrey code utilizing XOR gates 2772.4, while GBC 2780.4 shows anexemplary 4-bit conversion from Grey to binary code utilizing XOR gates2772.4. XOR gates 2772.4 may be implemented as discussed above inreference to FIG. 38D to minimize the amount of power utilized.

[0264] Another alternative implementation, in accordance with anembodiment of the present invention, for performing pulse widthmodulation includes a low frequency digital phase locked loop (DPLL)voltage controlled oscillator (VCO) with inverter stages and taps (i.e.,example 1 as listed above). FIG. 38H illustrates an exemplaryimplementation in accordance with this embodiment, which includes aphase frequency detector (PFD or phase detector) 2802.4, a charge pump2804.4, a loop filter 2806.4, a VCO 2808.4, and a frequency divider2810.4.

[0265] PFD 2802.4 receives a reference frequency (e.g., 32 kHz) on aline 2814.4 and a feedback signal from frequency divider 2810.4 on aline 2812.4 and determines whether to provide a pump up or a pump downsignal to charge pump 2804.4. Charge pump 2804.4 provides a signal,based on the pump up or the pump down signal to loop filter 2806.4 andVCO 2808.4. VCO 2808.4 is comprised of a ring oscillator having inverterstages and taps, as discussed similarly above in reference to FIG. 3,and therefore the description will not be repeated. An output signalfrom VCO 2808.4 is received by frequency divider 2810.4, which dividesdown a frequency of the output signal to a desired frequency to provideas the feedback signal.

[0266] Another alternative implementation for performing pulse widthmodulation may be viewed as a hybrid of a high frequency DPLL with acounter combined with a digital comparator (i.e., example 2 as listedabove) and a DPLL combined with a content addressable memory (i.e.,example 3 as listed above) to generate the required pulse widthmodulated signals.

[0267] More specifically, FIG. 38I illustrates a circuit 2900.4 toassist in generating pulse width modulation signals. Circuit 2900.4includes a decoder 2902.4 which controls logic gates 2904.4 for writingto memory 2906.4 (e.g., random access memory) having address lines (ADR)and data lines (D1). Memory 2906.4 stores data that determines start andstop times for desired pulse width modulated signals.

[0268] Memory 2906.4 provides data (at a DO terminal) under control of acontroller 2924.4 (through a read address (RA)) to multiplexers 2912.4,exclusive OR (XOR) gates 2910.4, and multiplexers 2918.4 viamultiplexers 2908.4. Under direction of controller 2924.4, XOR gates2910.4, multiplexers 2912.4 and 2918.4, registers 2914.4 and 2920.4, andadder/subtractor 2916.4 determine the data to provide to a comparator2922.4 to compare with a reference count 2926.4. Comparator 2922.4,which is similar to comparator 2310.4 of FIG. 36A, provides an outputsignal to a pulse width modulation circuit (i.e., PWM circuit 2314.4 asdescribed in reference to FIG. 36A). Consequently, by using memory and acomparator, pulse width modulated signals can be generated.

Section 1.1.6 Discussion of Phase Offset Tuning of Synchronous Drive toOptimize Conduction Losses vs. Dead Time

[0269] One of the efficiency optimizations in switching power suppliesis to attempt to minimize the power dissipated by the Schottky diodethat will typically either be inserted in the circuit across the lowertransistor (QB₁ in circuit 1301.2 of FIG. 46), or as is well known isintrinsic to a FET. In FIG. 46, the Schottky diode is indicated byreference character S1. In order to minimize the voltage drop acrossdiode S1, transistor QB₁ is inserted between terminal S and ground, andis turned on in some instances to reduce the voltage drop across diodeSi, therefore substantially reducing the power dissipated by this diode.Of course, any of this power dissipated will not be delivered to theload and so is therefore a source of inefficiency. The challenge becomesminimizing the amount of time that diode S1 conducts. It is desirablethat diode SI conduct only a very small amount of time, however, if theswitching signals to QB₁ and QT₁ become too close in time, because ofthe time delay required to switch on and off, it's possible that bothtransistors might be on simultaneously which would not only be a hugeefficiency loss, but could potentially result in catastrophic circuitfailure due to the unlimited currents flowing directly from the inputsupply through QT₁ to QB₁ to ground. So the optimization then is to movethe gate signal for QB₁ as close as possible to the gate signal of QT₁,but without causing an overlap in conduction.

[0270]FIG. 39. illustrates the expected voltage at terminal S in FIG. 46for the switching timing diagrams immediately above it in the figures.It will be appreciated that the voltage at terminal S falls as the gatedrive to QT₁ is turned off and drops to the point where it is caught bythe Schottky diode S1, then in the subsequent time QB₁ is turned onpulling the voltage back up to the supply rail. This process happens inreverse order at the other end of the pulse where the gate for QB₁ isturned off. Current is again allowed to flow into diode S1, and thevoltage at terminal S falls below ground which results in wasted powerdissipated until QT₁ is turned on and the voltage at terminal S switchesup to the positive supply rail and the cycle repeats.

[0271] In prior art solutions, a guard band must be constructed betweenthe timing of these two gate signals. This guard band has to be longenough to accommodate the slowest transistor that might be used in theapplication. In the present invention, in one embodiment we use dataprovided by the designer of the power supply being regulated byswitching power supply controller 1200 and program that data intointernal memory of switching power supply controller 1200, stating whatthe characteristics of the external transistors are. Accordingly, afixed guard band and time are not required. In a first embodiment, weuse the minimum number that could be used based on the published datafor the individual devices, and store the phase offset values in REGhw.In another embodiment of the present invention, we dynamically optimizethis further. This can be done by observing the efficiency of the givenoutput stage. For example, we know that for a buck power supply, theoutput voltage is equal to the duty cycle multiplied by the input supplyvoltage. Any deviation of the actual output voltage from that calculatedoutput voltage will be due to parasitic effects of inductors, resistors,capacitors, and the transistors themselves. It is therefore possible tocarefully, and at a slow rate over many cycles, tune the timing betweenQT₁ and QB₁ until this efficiency peaks and begins to degrade. It willdegrade rapidly as the transistors overlap, but this permits dynamicadaptation of the timing of the gate drive signals to the transistors tothe actual devices in the circuit being regulated. Switching powersupply controller 1200 can have a number of guard bands on a circuit tocircuit basis because the switching times of these transistors are alsosomewhat dependent on the load current that they are supplying and thetemperatures at which they are operating. The required amount of phaseoffset between the time QT₁ turns off and QB₁ turns on and the phaseoffset between when QB₁ turns off and QT₁ turns on may be different.Accordingly, fine tuning on both can be made. Temperature data isavailable to the controller from the Kelvin temperature sensor locatedin internal voltage supply 1209. In the first embodiment describedabove, providing the rise and fall time parameters for the transistorsto the controller can achieve a significant improvement over the priorart worst case tolerance scheme which does not take into account thespecifications of the actual transistors being used. In the secondembodiment, efficiency can be further improved by dynamically adaptingto the devices that are used, and thus achieving the highest efficiencypossible for the given set of transistors and discrete outputcomponents.

Section 1.1.7 Synchronous sampling Multiple Output

[0272] Sample and Hold Module (SHM) 1207 samples various voltages andcurrents and holds them until analog to digital converter 1206 is readyto receive them. As noted herein, analog input signals used in thecontrol loops are provided by Digital Pulse Converter 1201 via SHM 1207,and are converted to digital signals by analog to digital converter1206. As an example, SHM 1207 samples and holds thirteen voltages andseven currents, with seven voltages associated with external powersupplies being controlled or driven, two voltages associated withSUPPLYA and SUPPLYB and four auxiliary voltages: VOUT from KelvinTemperature Sensor 3516.4, and three pads TEMPEXT, AUX0 and AUX1

[0273]FIG. 40 is a functional block diagram of SHM 1207 in oneimplementation. The functional block diagram includes an input/output(I/O) circuit 3008.4, a voltage divider (scalar) 3010.4, a multiplexer3012.4, and a multiplexer 3016.4. An external voltage is sampled by I/Ocircuit 3008.4 via a pad 3000.4, with an output signal (OUTV) providedto voltage divider 3010.4. Voltage divider 3010.4 divides down or scalesthe output signal (OUTV) to an acceptable level under control of ascale[3:0] signal received from regulation control module (REG) 1204.For example, an external voltage (e.g., 15 V or less) is scaled to anappropriate value for analog to digital converter 1206 (e.g., inputrange of 0 to 3.3. V).

[0274] I/O circuit 3008.4 receives a SSUP signal and a SELVX signal fromregulation control module (REG) 1204 and an AUX signal and a SCLKVXsignal from DPC 1201. The AUX signal provides a sample clock forsampling one or more external supply voltages. The SSUP signal providesa select clock for selecting which external supply voltage to sample.The SCLKVX signal corresponds to SMPA[6:0] signal 2450.4 and SMPB[6:0]signal 2448.4, which control the sampling (and holding) of analogvoltages in SHM 1207 for analog to digital converter 1206. The SELVXsignal provides a select clock for selecting which external voltage tosample. An IDDQ signal provided to I/O circuits 3008.4 and 3016.4indicates a test control signal for these circuits.

[0275] An external current is sampled by I/O circuit 3016.4 via pads3002.4 and 3006.4 and utilizing a resistor 3004.4 connected between pads3002.4 and 3006.4, with an output signal (OUTC) provided. I/O circuit3016.4 receives an SWCAP[2:0] signal and an SELIX signal from regulationcontrol module (REG) 1204 and an SCLKIX signal from DPC 1201. TheSWCAP[2:0] provides input control for a switched capacitive network,discussed further below. The SCLKIX signal corresponds to SMPA[6:0]signal 2450.4 and SMPB[6:0] signal 2448.4, which control the sampling(and holding) of analog voltages (and currents) in SHM 1207 for analogto digital converter 1206. The SELIX signal provides a select clock forselecting which external current to sample.

[0276] Multiplexer 3012.4, under control of a MXSEL[4:0] signal fromregulation control module (REG) 1204, selects which input is presentedto analog to digital converter 1206 as an output signal VINADC. Besidesthe input signals discussed above, multiplexer 3012.4 also receives aVOUT signal from a Kelvin temperature sensor and a COUL0 and a COUL1signals, which are, Coulombmetric measurements from available batterysupplies (e.g., battery zero and battery one, discussed further herein).

[0277]FIG. 40A is a functional schematic illustrating an exemplaryimplementation for I/O circuits 3008.4 and 3016.4. An external voltageor current is sampled via a pad 3030.4 and electrostatic dischargeprotection (ESD) circuitry 3032.4, with the sampled signal passingthrough a pass gate 3034.4 to a logic circuit 3036.4. Logic circuit3036.4 buffers or scales the sampled signal, for example, prior toproviding it to a capacitor 3038.4, which acts as a holding capacitoruntil a pass gate 3040.4 is opened and the sampled signal is provided toanalog to digital converter 1206 via a lead 3042.4 (labeled OUTV or OUTCfor output voltage or output signal from switched capacitor network).

[0278] In terms of general operation, the select clocks (i.e., theSCLKIX, SCLKVX, and AUX signals from DPC 1201) control pass gate 3034.4for allowing an input voltage to charge capacitor 3038.4. The selectlines (i.e., the SELIX, SELVX, and SSUP signals from regulation controlmodule (REG) 1204) present the value stored on capacitor 3038.4 to bescaled (e.g., by voltage divider 3010.4) and passed to analog to digitalconverter 1206. If current is being measured, capacitor 3038.4 becomespart of a switched capacitor network to multiply a sampled input voltage(i.e., across resistor 3004.4) to a desired value for conversion byanalog to digital converter 1206.

[0279]FIG. 40B is a circuit schematic illustrating exemplary voltage andcurrent selection. An SHWIREI signal, an SHWIREV signal, and an SNHREFsignal is provided via pads 3060.4, 3062.4, and 3064.4 respectively. TheSHWIREI signal, SHWIREV signal, and SNHREF signal represent signals tobe measured by I/O circuits 3008.4 and 3016.4 (FIG. 40) forcorresponding current, voltage, and ground reference. As illustrated,the SCLKIX and SCLKVX signals control corresponding pass gates 3066.4,3072.4, 3076.4, and 3080.4 to allow an input voltage to charge acorresponding capacitor 3084.4 or 3086.4. The SELIX and SELVX signalscontrol corresponding pass gates 3068.4, 3074.4, 3078.4, and 3082.4 toallow the charge on corresponding capacitors 3084.4 or 3086.4 to pass asan output signal (labeled VOUTV or VOUTC for sampled voltage or current,respectively).

[0280]FIG. 40C is an exemplary interface signal block diagram for SHM1207 in accordance with another implementation. The interface signalsinclude an IDDQ signal 3700.4, an AUX0 signal 3702.4, an AUX1 signal3704.4, a TEMPEXT signal 3706.4, a VOUT signal 3708.4, a SUPPASENSEsignal 3710.4, a SUPPBSENSE signal 3712.4, a SHWIREI[6:0] signal 3714.4,a SHWIREV[6:0] signal 3716.4, an SMPA[6:0] signal 3720.4, an SMPB[6:0]signal 3722.4, an SHNREF[9:0] signal 3724.4, a SELA[12:0] signal 3726.4,a SELB[6:0] signal 3728.4, a DIV[2:0] signal 3730.4, a SHM_CLK signal3732.4, a MUXSEL[1:0] signal 3734.4, a DONE signal 3738.4, aVSEL_SMPA[8:0] signal 3740.4, a ISEL_SMPA[6:0] signal 3742.4, aVREF_HALF signal 3748.4, a VSSIOA/B signal 3750.4, a VSS signal 3752.4,an AVS signal 3754.4, a VINADC signal 3758.4, an AVD signal 3760.4, aVDD signal 3762.4, and a VDDIOA/B signal 3764.4. Pads 3718.4 indicatesignals received external to switching power supply controller 1200.

[0281] IDDQ signal 3700.4 is a test signal, while AUX0 signal 3702.4 andAUX1 signal 3704.4 are external signals for auxiliary applications.TEMPEXT signal 3706.4 is received from a temperature sensor circuitattached to the external battery. VOUT signal 3708.4 represents thevoltage from the Kelvin temperature sensor (e.g., Kelvin temperaturesensor 2232.4 in FIG. 54) that will be sampled and held to isolate itsground from the ground of analog to digital converter 1206 when thisvoltage gets converted.

[0282] SUPPASENSE signal 3710.4 and SUPPBSENSE signal 3712.4 are used tosense the voltage on the external Supply A and Supply B power supplies.SHWIREI[6:0] signal 3714.4 is used for sensing the voltage drop across asense resistor for each of the 7 external power supplies. SHWIREV[6:0]signal 3716.4 is used for sensing the voltage for each of the 7 externalpower supplies. SHNREF[9:0] signals 3724.4 are ground references forboth the voltage and the current of each external power supply, plus.there are three additional references for Supply A, Supply B, AUX0signal 3702.4, AUX1 signal 3704.4, and TEMPEXT signal 3706.4.

[0283] SMPA[6:0] signal 3720.4 is received from DPC 1201 and is used forsampling voltages at the load of the seven power supplies. SMPB [6:0]signal 3722.4 is received from DPC 1201 and is used for sampling thevoltage drop across the sense resistor for the seven supplies (describedin further detail below). SELA [12:0] signal 3726.4 is received fromregulation control module (REG) 1204 and determines which channelvoltage needs to be presented to a divider 3804.4 (FIG. 40D). SELB [6:0]signal 3728.4 is received from regulation control module (REG) 1204 anddetermines which channel current measurement.

[0284] VSEL_SMPA[8:0] signal 3740.4 is received from regulation controlmodule (REG) 1204 and determines the swapping of the sample pulses forthe leading edge. ISEL_SMPA[6:0] signal 3742.4 is received fromregulation control module (REG) 1204 and determines the swapping of thesample pulses for the falling edge.

[0285] DONE signal 3738.4 is received from analog to digital converter1206 when it is done with a conversion. DIV[2:0] signal 3730.4 isreceived from regulation control module (REG) 1204 and determines thedivider value of divider 3804.4 for the voltage.

[0286] SHM_CLK signal 3732.4 is received from CLKGEN 1223, with afrequency that is 16 times the frame frequency and is the valuegenerated in CTS[4] within DPC 1201 as explained elsewhere herein.MUX_SEL [1:0] signal 3734.4 is used for selecting an output signal for amultiplexer 3806.4 (FIG. 40D, e.g., an analog mux) that will bepresented to analog to digital converter 1206. VDDIOA/B signals 3764.4are the highest voltages needed for substrate connection when using highvoltage switches. VSSIOA/B signals 3750.4 are the lowest voltages neededfor substrate connection when using high voltage switches.

[0287] VDD signal 3762.4 (e.g., 3.3 V) is a digital voltage required forsome control logic. VSS signal 3752.4 is a digital ground required forsome control logic. AVD signal 3760.4 (e.g., 3.3 V) is an analog voltagerequired for some control logic. AVS signal 3754.4 is an analog groundto be tied to a ground of analog to digital converter 1206 whenconverting values into analog to digital converter 1206. VINADC signal3758.4 is provided to analog to digital converter 1206, for example,with a range between 0 and 3.0 V. VREF_HALF signal 3748.4 is a voltageoffset needed for a multiplier (discussed in detail below) to measureeither positive or negative voltage differences across analog to digitalconverter 1206. The value of VREF_HALF signal 3748.4 is one-half that ofVREF signal 3440.4 (FIG. 54A) and is received from IVS 1209. Theinterface signals are summarized in Table 1.1.7a. TABLE 1.1.7a I/FSignal Type Description Source Destination IDDQ Input Test input ifneeded ITS [#] AUX0 Input I/O PAD auxiliary Chip I/O sample AUX1 InputI/O PAD auxiliary Chip I/O sample TEMPEXT Input I/O PAD external tempChip I/O VOUT Input I/O PAD internal temp Chip I/O SUPPASENSE Input I/OPAD Supply A Chip I/O SUPPBSENSE Input I/O PAD Supply B Chip I/O SHWIREI[6:0] Input I/O PAD for current Chip I/O sample SHWIREV [6:0] Input I/OPAD for voltage Chip I/O sample SMPA [6:0] Input Sample pulse for DPC1201 leading edge SMPB [6:0] Input Sample pulse for DPC 1201 fallingedge SHNREF [9:0] Input I/O PAD ground Chip I/O reference SELA [12:0]Input Select leading edge REG 1204 (voltages) SELB [6:0] Input Selectfalling edge REG 1204 (current) DIV [2:0] Input Select divider value REG1204 SHM_CLK Input CLK for sampling CLKGEN [#] MUXSEL [1:0] Input AnalogMux Select REG 1204 DONE Input ADC conversion ADC 1206 finishedVSEL_SMPA [8:0] Input Selects leading edge REG 1204 swap ISEL_SMPA [6:0]Input Selects falling edge REG 1204 swap VDDIOA Input I/O Power for HVIVS 1209 transistors VDDIOB Input I/O Power for HV IVS 1209 transistorsVSSIOA Input I/O Ground for HV IVS 1209 transistors VSSIOB Input I/OGround for HV IVS 1209 transistors AVS Input Analog Ground IVS 1209 AVDInput 3.3 V Analog Power IVS 1209 VINADC Output Data for the ADC ADC1206 VDD Input Global Digital 3.3 V VSS Input Global Ground 3.3 VVREF_HALF Input 1/2 VREF for the IVS 1209 Multiplier

[0288]FIG. 40D is a functional block diagram 3788.4 of SHM 1207 inanother implementation. FIG. 40D is similar to FIG. 40 and therefore adiscussion regarding general operation will not be repeated. Blockdiagram 3788.4 of FIG. 40D includes an I/O circuit 3800.4, a multiplexer3802.4, a divider 3804.4, a multiplexer 3806.4, an I/O circuit 3810.4,and multiplexers 3808.4, 3820.4, and 3822.4.

[0289] The general function of block diagram 3788.4 is to sample ninevoltages, seven of them being the external output voltage supplies andtwo of them being the Supply A and the Supply B, and also to sample thevoltage difference across a sense resistor (represented by a senseresistor 3814.4 in FIG. 40D) for measuring current in each of the seven“regulated” output voltage supplies. Additionally, there are a fewsignals that are sampled on an as needed basis, for example, the voltageentering switching power supply controller 1200 as a result of atemperature sensor system that is connected to the battery (i.e., thevoltage of VOUT SIGNAL 3708.4), an internal voltage coming from Kelvintemperature sensor 2232.4 (FIG. 54) and the voltages of TEMPEXT signal3706.4, AUX0 signal 3702.4 and AUX1 signal 3704.4.

[0290] In general, block diagram 3788.4 interfaces with DPC 1201,regulation control module (REG) 1204, and analog to digital converter1206 and receives from external sources three analog inputs (via pads3818.4, 3816.4, and 3812.4) that can be up to 15 V (e.g., for PDAs) or16 V (e.g., for digital cameras). As shown in FIG. 40D, I/O circuits3800.4 and 3810.4 are coupled together to sample both voltage andcurrent at the same time, and convert these measurements at differenttimes as needed.

[0291] Multiplexer 3820.4 under control of ISEL_SMPA[6:0] signal 3742.4selects a signal from SMPA[6:0] signal 3720.4 and SMPB[6:0] signal3722.4 and generates an SMPI signal 3821.4 for I/O circuit 3810.4.Multiplexer 3822.4 under control of VSEL_SMPA[8:0] signal 3740.4 selectsa signal from SMPA[6:0] signal 3720.4 and SMPB[6:0] signal 3722.4 andgenerates an SMPV signal 3823.4 for I/O circuit 3800.4.

[0292]FIG. 40E illustrates an exemplary block diagram for I/O circuits3800.4 and 3810.4 in one implementation, which includes a number oftransmission gates 3824.4 and 3830.4, ESD protection 3825.4.4, one ormore capacitors 3828.4, along with a logic circuit 3826.4 having a testmechanism (via IDDQ signal 3700.4). FIG. 40E is similar to FIG. 40A andtherefore the general operation will not be repeated.

[0293] As shown in FIG. 40E, SHWIREI signal 3716.4 represents a voltagesignal to be measured across sense resistor 3814.4 (FIG. 40D). As anexample for sampling a current, a switched capacitor network will beutilized for the multiplication to be done for each of the sevencurrents explicitly (discussed in further detail below). SHWIREV signal3714.4 represents a voltage signal to be measured, and SHNREF signal3724.4 represents a voltage signal for a ground reference. The Supply Aand the Supply B, along with TEMPEXT signal 3706.4 and VOUT signal3708.4, will be measured using a combination of SHWIREV signal 3714.4and SHNREF signal 3724.4 to sample and measure the voltages.

[0294]FIG. 40F is an exemplary circuit schematic illustrating voltageand current selection for another implementation and may be viewed as anexpanded view of a portion of FIG. 40E. In terms of general operation(in reference to FIG. 40D and 1.1.7 g), the three basic analog inputsignals is as follows. When there is a sample pulse for SMPV signal3823.4, a measured voltage between pads 3816.4 and 3818.4 is stored in aholding capacitor 3858.4 as the voltage measurement at the load.

[0295] When there is a sample pulse for SMPI signal 3821.4, a measuredvoltage between pads 3812.4 and 3816.4 is stored across capacitors3856.4, arranged in a parallel fashion by appropriate switching of passgates 3840.4, which represents the voltage measured across senseresistor 3814.4. Note that the voltage difference across sense resistor3814.4 can be positive or negative depending on the external powersupply topology.

[0296] When a SELA signal corresponding to SELA[12:0] signal 3726.4 isasserted, the voltage in holding capacitor 3858.4 gets transferred intovoltage divider 3804.4 as a VOUTV signal 3912.4. When there is a SELBsignal corresponding to SELB[6:0] signal 3728.4, capacitors 3856.4 arestacked serially, by appropriate switching of pass gates 3840.4, toperform voltage multiplication (e.g., multiplication of 4) and provide aVOUTC signal 3859.4. The reference for the voltage multiplication isdone with respect to VREF_HALF signal 3748.4.

[0297] Divider 3804.4 divides the voltage down to a range of 0 to 3 V sothat it is within desired limits and analog to digital converter 1206can read the value. Divider circuitry for divider 3804.4 will beimplemented, for example, using capacitor ratios with switches, twonon-overlapping clocks, and control logic. The non-overlapping clocksdischarge the capacitance of the divider network and prepare the dividernetwork for the next voltage sample.

[0298]FIG. 40G is an exemplary clock generation circuit in accordancewith another implementation. The two non-overlapping clocks, a DCLKHsignal 3884.4 and a DCLKL signal 3886.4, will be implemented byemploying two RS latches 3876.4 and 3878.4 and control logic, such aswith an AND gate 3880.4 and an OR gate 3882.4. The clock generationcircuit receives DONE signal 3738.4, SHM_CLK signal 3732.4, and DIV[2:0]signal 3730.4, as shown, to produce DCLKH signal 3884.4 and DCLKL signal3886.4. Table 1.1.7b provides exemplary divide or scalar values forgiven input voltages to produce representative values from analog todigital converter 1206. TABLE 1.1.7b Divide Values (Scalar InputVoltages integers) (Voltage) ADC Value 1 0.498-2.502 166-834 22.508-5.502 418-917 4  5.508-11.508 459-959 6 8.520-17.91 640-995

[0299] As an example, the maximum input voltage stored in holdingcapacitor 3856.4 is 16 V. Depending upon the type of capacitor used(e.g., PiP capacitors can only withstand 13.5 V), two or more capacitorsmay be stacked in accordance with an implementation of divider 3804.4.

[0300]FIG. 40H is an exemplary voltage divider 3898.4 in accordance withanother implementation for voltage divider 3808.4. VOUTV signal 3912.4is a selected channel voltage and switches 3900.4, 3902.4, 3904.4,3908.4, 3910.4, and 3912.4 are controlled by the non-overlapping clocks(DCLKH signal 3884.4 and DCLKL signal 3886.4) as shown. For example,because there are four values for division (i.e., divide values in Table1.1.7b), the default will be a divide by 1 which will allow VOUTV signal3912.4 to pass through directly, with DIV[2:0] signal 3730.4 set tologic 0. Voltage division is accomplished by charge sharing acrosscapacitors. Different effective capacitor values can be selected bytransfer gates 3900.4, 3902.4 and 3904.4 and their associated capacitors3914.4, 3916.4 and 3918.4. The DIV[2:0] determines which transfer gatesare selected to achieve the divide ratios. Table 1.1.7c providesexemplary divide values based on DIV[2:0] signal 3730.4. TABLE 1.1.7cDivide DIV[2] DIV[1] DIV[0] Value 0 0 0 1 0 0 1 2 0 1 0 3 0 1 1 4 1 0 03 1 0 1 4 1 1 0 5 1 1 1 6 (default)

[0301] I/O circuit 3810.4 (FIG. 40D) includes( a switched capacitornetwork to provide voltage multiplication for a measured voltagedifference across sense resistor 3814.4 for a corresponding currentmeasurement. For example, in a continuous mode of operation at 2A andusing a 0.1 ohm resistor for sense resistor 3814.4, the voltagedifference across sense resistor 3814.4 is 200 mV. Thus, voltagemultiplication based on the desired voltage parameters is desirable.Furthermore, because the external battery may be charging itself fromanother power supply configuration, the current sense may be negativewith respect to the ground of analog to digital converter 1206 and themultiplier circuit, illustrated below in reference to FIG. 40I, has thecapability of reversing polarities to always present a positive voltagedifference to the ADC.

[0302] Table 1.1.7d provides exemplary current measurements for a 2Apower supply system with a 0.1 ohm resistance for sense resistor 3814.4(where D.C.S. and C.S. stand for Deep Cycle Skipping and Cycle Skipping,respectively). TABLE 1.1.7d Current Mode Method Voltage 4× 300 uA D.C.S.Dv/Dt 30 uV 120 uV 3 mA C.S. Dv/Dt 300 uV 1.2 mV 30 mA DiscontinuousDigital 3 mV 12 mV 2 A Continuous Direct 200 mV 800 mV

[0303]FIG. 40I is an exemplary voltage multiplier 3928.4 in accordancewith another implementation for I/O circuit 3810.4. Voltage multiplier3928.4 includes pass gates 3930.4 and capacitors 3934.4. In terms ofgeneral operation, when a sampling pulse from SMPI signal 3821.4 isreceived, capacitors 3930.4 are arranged in parallel by pass gates3930.4. When a SELB signal of SELB[6:0] signal 3728.4 is asserted,capacitors 3934.4are stacked in series via pass gates 3930.4 andconnected between either positive or negative with respect to VREF_HALFsignal 3748.4. It should be noted that no matter what the polarity isfor the voltage drop, it will not affect the measurements since thereference is not ground but an offset voltage provided by VREF_HALFsignal 3748.4.

[0304] Because there is a 4× multiplication done at once for eachcurrent measurement channel (i.e., for the different currentmeasurements for each power supply), there will be 7 multipliers, withone for each external power supply. FIG. 40J illustrates an exemplaryblock diagram of I/O circuit 3810.4 with various interface signalsshown.

[0305] Multiplexer 3806.4 (FIG. 40D) employs high voltage switches andcare needs to be taken so that divider 3804.4 does not present a highvoltage via multiplexer 3806.4 to analog to digital converter 1206. FIG.40K is a multiplexer scheme in accordance with another implementationthat mitigates the threat of a high voltage being presented to analog todigital converter 1206. As shown, SHM_CLK signal 3732.4 is gated withDIV[2:0] signal 3730.4, by an AND gate 4002.4, to properly present aDIVOUT signal 4010.4 from divider 3898.4 or VOUTC signal 3859.4 toanalog to digital converter 1206 (not shown) via a multiplexer 4008.4and VINADC signal 3758.4.

Section 1.2 Discussion of the Voltage Regulator, Detailed Hardware,Operations and Optimizations

[0306]FIG. 11 shows an alternative structure for implementing theprinciples of this invention. In FIG. 11, controller 111 detects thecurrent through resistor R and the voltage across load capacitor CL. Thecharge on load capacitor CL is used to drive a load on lead 112. Thecontroller 111 produces an error signal proportional to the voltagedifference between the voltage across capacitor CL and a referencevoltage, shown as system ground, but which could be any other desiredreference voltage. The output signal from controller 111 is supplied toan A to D converter 113 having ten output bits. This allows 1,024 levelsto be identified and quantized. The ten output bits from the A to Dconverter are sent on 10-bit bus 114 to comparator 115 where these bitsare compared to a reference number driven from programmable reference116. Reference 116 is programmed by the user to contain the desiredreference voltage to be held by load capacitor CL. The output signalfrom comparator 115 is a binary difference signal D0 through D9 which istransmitted on 10-bit bus 117 to phase select circuit 118. Phase selectcircuit 118 is of the type, for example, shown above in FIG. 6. Thesignals D0 through D9 from comparator 115 are decoded using a circuitryof a type shown, for example, in FIG. 10 and are used to generate asignal which controls a pass transistor which allows a selected outputsignal from an inverter in the ring oscillator to be applied to the redinput lead 119 a of exclusive OR gate 119. The green input lead 119 b,as described above, will typically be the output signal pulled from thefirst inverter in the ring oscillator string. The result is a pulsewidth modulated output signal on lead 119 c from exclusive OR gate 119,which is then used to charge capacitor CL through resistor R (FIG. 11).The current through resistor R is measured by a signal detected on leads111 a and 111 b and used in controller 111 to provide a measure of thecharge being provided to load capacitor CL.

[0307] Analog to digital converter 1206 (FIG. 12), which measures anddigitizes the voltage of an analog signal to 10-bits of resolution, canbe implemented by a combination of a custom low-power mixed-signalcircuit (ADC) and a digital logic circuit for interfacing the ADC toexternal logic circuits. Inputs and output signals to analog to digitalconverter 1206 include both analog and digital signals. In oneimplementation, the analog to digital conversion can operate at 10 Msps(i.e., Mega-samples per second).

[0308]FIG. 14 is a block diagram showing interface signals of analog todigital converter 1206, according to one implementation. As shown inFIG. 14, analog to digital converter 1206 includes: (a) analogmeasurement interface (AMI) 1401, digital interface (DI) 1402, and powersupply interface 1403. Analog measurement interface 1401 includes analoginput signal 1401 a (VIN), which is sampled for analog to digitalconversion, and an analog voltage reference input signal 1401 b (VREF).

[0309] Digital interface 1402 comprises data output bus 1402 a(DOUT[9:0]), analog to digital conversion completion or “done” signal1402 b (DONE), analog to digital conversion initiation plus reset signal1402 c (START/RSTN), and clock signal 1402 d (CLK). In thisimplementation, data output bus 1402 a is a 10-bit bus which providesthe result of the analog to digital conversion. In this implementation,clock signal 1402 d has a frequency of about 128 MHz and a duty cycle ofabout 50%. When the asynchronous reset signal 1402 e is held at a lowlogic value, circuits in analog to digital converter 1206 are held in areset state. Similarly, when power down signal 1402 f is held at a lowlogic value, the analog circuits in analog to digital converter 1206 arepowered down, and the digital logic circuits are placed in a low-powerstate.

[0310] Power supply interface 1403 includes analog power and groundreferences 1403 a and 1403 b (AVD and AVS), and digital power and groundreferences 1403 c and 1403 d (VDD and VSS), respectively. In oneimplementation, both the analog and the digital power references (i.e.,AVD and VDD) are provided at 3.3V±10%.

[0311]FIG. 15 is a block diagram showing the interface signals of kelvintemperature sensor (KTS) 1500, which is an absolute temperature sensorcircuit that produces an output voltage linearly related to theCIRCUIT'S absolute temperature. As shown in FIG. 15, Kelvin temperaturesensor 1500 receives analog power and ground reference voltages atterminals 1501 and 1502 and asynchronous power-down control signal (PDN)at terminal 1503, and provides output voltage VOUT at terminal 1504,which is linearly related to the temperature of the circuit between 0.0Vand 3.0V.

Section 1.2.1 Hardware Description Regulation Control Module (REG) 1204Combined Section 1.2.1.1 Detailed Description of the REG Module andSection 1.2.1.2 Voltage/Current Feedback SPS—Hardware Portion

[0312] Referring now to FIG. 41 and FIG. 12, Regulation control module(REG) includes a microcontroller 500.1 configured to generate pulsewidth modulation (PWM) information for a plurality of switching powerconverters under the control of switching power supply controller 1200.This PWM information may include the switching times for power switcheswithin the PWM switching power converters as well as voltage and currentsampling times for each switching power converter. Regulation controlmodule (REG) provides the PWM and sample information to Digital Signalto Pulse Converter (DPC) 1201, which in turn generates signalscontrolling pulse rising and falling edges to implement the PWMinformation, as well as generating the sample pulses for voltage andcurrent sampling.

[0313] As described further herein, DPC 1201 may be implemented in anumber of ways, e.g., it may be CAM-based, ring-oscillator-based,comparator-based, or RAM-based. The following description will assumethat DPC 1201 is in the CAM-based embodiment. However, it will beappreciated that regulation control module (REG) 1204 would operateanalogously should DPC 1201 have a non-CAM-based embodiment.

[0314] The frame rate implemented by DPC 1201 affects the requiredprocessing speed of microcontroller 500.1. A DPC frame is illustrated inFIG. 37. For example, if seven switching power supplies are beingcontrolled by switching power supply controller 1200 and the DPC framerate is 524 KHz, the PWM information for each switching power convertermay be updated approximately every 2 microseconds, which is thecorresponding DPC frame period. Accordingly, a regulation schedulermodule 521.1 may divide each DPC frame period into calculation periodscorresponding to the various switching power supplies being regulated soas to implement a pipelined timeslot-based approach to the calculationsfor the PWM updates and voltage and current feedback conversionscheduling for each switching power supply under control. In addition,another calculation period may be required for each DPC frame forrelated calculations with respect to “book-keeping” tasks, and themonitoring of the various power supplies for the switching powersupplies being regulated. Thus, should there be seven switching powersupplies under control at a DPC frame rate of 524 KHz, there would beeight 250 ns timeslots (7 power supplies+1 slot for bookkeeping). Thus,the microcontroller 500.1 would have only 250 nanoseconds to calculatethe PWM information (pulse width) for each of the seven switching powersupplies. Regulation scheduler module 521.1 receives switching powersupply controller 1200 clock signal 522.1 and CST signals 2458.4 andcoordinates the timing of the various modules within regulation controlmodule (REG) 1204 accordingly. If each calculation period may becompleted in 32 arithmetic steps (corresponding to 32 cycles of internalclock 522.1), microcontroller 500.1 would require an instructionexecution rate of 128 MHz. The arithmetic functions implemented in eachinstruction may include, for example, any of add, subtract, multiply,magnitude comparison, and absolute value. Microcontroller 500.1 may beimplemented using any of a number of architectures to achieve therequired operation speed, including a RISC-based or a VLIW-basedarchitecture (i.e., “reduced instruction set computer” basedarchitecture or “very-long-instruction word”-based architecture). Forexample, in a VLIW-based embodiment, microcontroller 500.1 may include aVLIW computing engine 517.1 that interfaces with a decode ROM (i.e.,read-only memory, not illustrated) for decoding the VLIW instructions.In addition, microcontroller 500.1 may include a RAM 516.1 for storingdata and parameter values. Register files 518.1 store the regulationparameter values for the various switching power supplies underregulation and provides run-time register resources for calculationstaking place in VLIW engine 517.1. In one embodiment, VLIW engine 517.1includes a topology register which points to the beginning of a32-instruction segment in memory (corresponding to the number ofinstructions that can be executed within a time slot). The topologyregister is so-named as the regulation algorithm for each topology(e.g., buck, boost, SEPIC) can be stored at different 32-instructionsegments in memory. In addition, a 5-bit program counter can be providedfor sequencing VLIW engine 517.1 through the 32-instruction segment inmemory.

[0315] Referring again to FIG. 37, for a given switching powerconverter, regulation control module (REG) 1204 computes the timings forthe rising and falling edges for a PFET pulse 2410.4 and an SFET pulse2412.4. The rising edge and falling edge of PFET pulse 2410.4 controlthe on and off times, respectively, of a given switching powerconverter's primary FET switch as driven by NFET driver module 1202.Similarly, the rising edge and falling edge of SFET pulse 2412.4 controlthe on and off times, respectively, of the given switching powerconverter's secondary FET switch as driven by NFET driver module 1202.The rising edge and falling edge of SMPA pulse 2414.4 may control thevoltage sampling period used by sample and hold module (SHM) 1207 toobtain voltage feedback information from the corresponding switchingpower converter. Similarly, the rising edge and falling edge of SMPBpulse 2416.4 may control the current sampling period used by SHM 1207 toobtain current feedback information from the corresponding switchingpower converter. However, either pulse SMPA 2414.4 or SMPB 2416.4 may beused for voltage or current feedback purposes.

[0316] The four pulses illustrated in FIG. 37 thus correspond to eightindependent rising and falling edge times. For example, the falling edgeof SMPA pulse 2414.4 may be programmed to coincide with the rising edgeof PFET pulse 2410.4 (PFTS), because SMPA pulse 2414.4 can be requiredto be completed no less than 150 nano-seconds prior to the rising edgeof PFET 2410.4. (This relationship allows sufficient time formicroprocessor 500.1 to calculate the required duration of PFET pulse2410.4 using the data sampled by SHM 1207 using SMPA pulse 2414.4 andconverted by analog to digital converter 1206.) Similarly, the fallingedge of SMPB pulse 2416.4 may be programmed to coincide with the fallingedge of PFET pulse 2410.4 (PFTR), thereby allowing sampling of the peakcurrent in external inductor that occurs immediately prior the fallingedge of PFET pulse 2410.4. The widths of sampling pulses (i.e., SMPApulse 2414.4 and 2416.4) can be programmed, for example, at 2 or 4nanoseconds. Because at least 50 nanoseconds are to be provided betweensampling a pulse and a transition in the PFET and SFET pulses, theeffective duty cycle range computed by microprocessor 500.1 is 10% to90%. Duty cycles of 0% or 100% can be achieved in the DPC by masking theedge transitions of the PFET or SFET pulses, as needed.

[0317] Regardless of the number of independent pulse edges regulationcontrol module (REG) 1204 must control, other objectives besides powerregulation may affect the scheduling of the various pulse rising andfalling edges for each controlled switching power converter within a DPCframe. For example, having two switching power supplies switchsimultaneously may generate electromagnetic interference (EMI) or otherundesirable effects. In addition, simultaneous switching output (SSO)requirements may limit the number of FETS that may be switched at anygiven time. Accordingly, regulation control module (REG) 1204 mayschedule the various pulse rising and falling edges to satisfy suchobjectives using an edge scheduler 510.1. As described above,microcontroller 500.1 may implement a pipelined regulation approach suchthat each DPC frame is divided into calculation periods to calculatepulse width information 505.1 for each switching power supply controlledby switching power supply controller 1200. In a given DPC frame, thenecessary calculations to update PWM and schedule the digitization ofthe related analog voltage and current feedback signals are performedwith respect to the preceding DPC frame. If SHM clock signal 3732.4 hasa frequency {fraction (1/16)}^(th) that of SPS clock 522.1, two feedbacksignal analog-to-digital conversions may be accomplished per calculationperiod. Thus, a given DPC frame may be divided as follows: Slot 0 Slot 1Slot 2 Slot 3 Slot 4 Slot 5 Slot 6 Slot 7 IPC CALC SUP0 CALC SUP1 CALCSUP2 CALC SUP3 CALC SUP4 CALC SUP5 CALC SUP6 CONV SUP0 CONV SUP1 CONVSUP2 CONV SUP3 CONV SUP4 CONV SUP5 CONV SUP6 CONV SUPA CONV SUPB

[0318] Thus, during slot (or calculation period) 0, the conversions forthe voltage and current feedback signals for the zeroth switching powersupply occur. Then, VLIW engine 517.1 may perform the necessary PWMupdates to a register file 518.1 using the converted feedback signalsfor the zeroth switching power supply during calculation period 1. Then,DPC I/F 590.1 may perform the necessary PWM update using the convertedfeedback signals from the zeroth slot of the previous DPC frame. Inaddition, the conversions for the first switching power supply feedbacksignals may occur in calculation period 1. Then, VLIW engine 517.1 mayperform the necessary PWM updates to a register file 518.1 using theconverted feedback signals in the second calculation period, the DPC I/Fmay perform the PWM updates using the converted feedback signals fromthe first time slot of the previous DPC frame, and so on for theremaining switching power supplies. Note that in calculation period 7,an analog-to-digital conversion is made for the voltages of powerssupplies A and B. No corresponding calculation period need be scheduled(switching power supply controller 1200 does not regulate these supplyvoltages). Because these conversions occur in the seventh timeslot, thezeroth timeslot of the next DPC frame may be used by regulationscheduler 521.1 to schedule any required inter-process communication andbookkeeping. A separate state machine may be used to implement edgescheduler 510.1. Having received the pulse width information and samplecommands from microcontroller 500.1, edge scheduler 510.1 may thenschedule the various pulse rising and falling edges. For example,referring again to FIG. 37, each DPC frame may be divided into aplurality of counts, e.g., 1024 counts (from 0 to 1023). The timebetween these counts determines the maximum PWM resolution that may beimplemented. The various pulse edges may be scheduled according to thecounts a DPC frame is divided into. Thus, edge scheduling would compriseassigning each edge to a DPC frame count. A number of algorithms may beused to provide the appropriate edge scheduling. For example, should apulse edge from two switching power converters be scheduled for the samecount, edge scheduler 510.1 could delay one of the conflicting pulseedges by one or more counts. Sample pulses SPAS 2414.4 and SPBS 2416.4may be scheduled to have a rising edge one or more counts before therising edge and falling edges of PFET pulse 2410.4, respectively. Aspecial cycle skipping mode is enabled by the edge scheduler through aprogrammable register. This provides the ability to skip the generationof a PFET pulse during a specified cycle. This is accomplished bywriting the same value to DPC 1201 for rising and falling edges of PWMpulses thereby generating a 0% DC output for those pulses.

[0319] To minimize the need for edge scheduling, central processingmodule (SYS) 1205 initializes regulation control module (REG) 1204 withappropriate rising and falling edge schedules prior to normal operation.For example, central processing module (SYS) 1205 stores in memory thedesired voltage levels provided by the various switching powerconverters, the expected power drawn by the loads, and the associatedoperating characteristics such as inductances and capacitances used inthe switching power converters. From this information, centralprocessing module (SYS) 1205 may calculate an expected pulse width foreach switching power converter. In turn, central processing module (SYS)1205 may then assign pulse edges corresponding to these pulse widthsdistributed across a DPC frame to help reduce the need for edgescheduling. For example, assuming a pipelined approach has beenimplemented, the rising edge of PFET pulse 2410.4 for each switchingpower supply has been calculated by central processing module (SYS)1205. Central processing module (SYS) 1205 then provides these initialedge schedules and other information to regulation control module (REG)1204 through an internal bus 520.1, which in turn may comprise buses forSFR-mapped data as well as buses for memory-mapped data. A bus interface525.1 may be used to coordinate the flow of data between regulationcontrol module (REG) 1204 and central processing module (SYS) 1205 oninternal bus 520.1 and provide the coordinated data to microcontroller500.1. For example, internal bus 520.1 may comprise an SFR enable signalREG_SFR_EN 700.1 to indicate an SFR transaction is set to occur; an SFRaddress signal SFR_ADDR[7:0] 701.1; an SFR data out signalSFR_DATA_OUT[7:0] 702.1 from central processing module (SYS) 1205; anSFR write enable SFR_WR 703.1; an SFR read enable SFR_RD 704.1; an SFRdata out signal SFR_DATA_IN[7:0] 705.1 from central processing module(SYS) 1205; a memory-mapped enable signal REG_MEM_EN 706.1 to indicate amemory-mapped transaction is set to occur; a memory-mapped addresssignal MEM-ADDR[15:0] 707.1; a memory-mapped data out signalMEM_DATA_OUT[7:0] 708.1 from central processing module (SYS) 1205; amemory-mapped data write enable signal MEM_WR_N 709.1; a memory-mappeddata read enable signal MEM_RD_N 710.1; a memory-mapped data out signalMEM_DATA_IN[7:0] 711.1 from regulation control module (REG) 1204; a modesignal PD[1:0] 712.1, a REG-generated interrupt signal REG_INT 713.1;and the central processing module clock signal SYS_CLK 714.1. Bycoordinating the flow of these signals on internal bus 520.1, interfacemodule 525.1 allows central processing module (SYS) 1205 to configureregulation control module (REG) 1204 and monitor its operation.

[0320] Referring again to FIG. 12, regulation control module (REG) 1204receives digitized feedback information (representing voltage andcurrent samples) from each switching power converter from analog todigital converter 1206 as signal DOUT[9:0] 715. The analog voltage andcurrent samples digitized by analog to digital converter 1206 areprovided by SHM module 1207 based upon the rising and falling edge timescorresponding to pulses SPAS 2414.4 and SPBS 2416.4. Referring now toFIG. 40D, a multiplexer 3806.4 within SHM 1207 may select between thesampled-and-held voltages and provide the selected voltage to analog todigital converter 1206. To keep analog to digital converter 1206operating efficiently, a conversion scheduler 540.1 receives the timinginformation from signals SMPA 2406.4 and SMPB 2408.4 and commandsmultiplexer 3806.4 accordingly using MUX-SEL[1:0] signal 3734.4. Asdiscussed above, if a pipelined approach is implemented, two conversionsmay be accomplished for each calculation period in a DPC frame.Conversion scheduler 540.1 drives SHM module 1207 to perform therequired scaling of the analog feedback signals and properly schedulethe digitization of the converted values in analog to digital converter1206.

[0321] Analog to digital converter 1206 may respond to a START/RSTNsignal 586.1 from conversion scheduler 540.1 toggling LOW to HIGH tobegin the analog-to-digital conversion process for a given analogfeedback signal. During times of no active ADC activity, REG may pullSTART/RSTN signal 586.1 LOW to put analog to digital converter 1206 intoa low power mode. To keep the sampled voltages within the dynamic rangeof analog to digital converter 1206, conversion scheduler 540.1 providesa scalar variable, DIV[1:0] 3730.4, to SHM 1207 to provide theappropriate scaling. Conversion scheduler 540.1 may drive SHM 1207 toselect the appropriate voltage feedback signal for conversion throughselection signal SELA[12:0] 3726.4. Similarly, selection signalSELB[8:0] 3728.4 drives the appropriate selection of current feedbacksignals. Because each pulse SMPA 2406.4 or SMPB 2408.4 may be used foreither voltage or current feedback, conversion scheduler 540.1 indicateswhich pulse has been used for voltage or current feedback by signalsVSEL_SMPA[8;0] 3728.4 and ISEL_SMPA[6:0] 3742.2, respectively.

[0322] During a given DPC frame, multiplexer 3806.4 will begin toreceive the various sampled-and-held voltage and current feedbacksignals. Conversion scheduler 540.1 may simply cause multiplexer 3806.4to select the sampled-and-held feedback voltages as received in realtime. Alternatively, conversion scheduler 540.1 may delay the schedulingaccording to whether or not all the feedback information has beenreceived from a given switching power converter. For example, supposethe voltage feedback from a given switching power converter has beensampled-and-held and received by multiplexer 3734.4. Conversionscheduler 540.1 would not cause multiplexer 3734.4 to select thisvoltage feedback signal, however, until the corresponding currentfeedback signal has also been received at multiplexer 3734.4.

[0323] To allow sufficient setup time for SHM 1207 to properly latchdata, conversion scheduler 540.1 may switch the various SHM 1207 controlsignals described above one SPS clock cycle 522.1 before calculationperiod boundaries within a given DPC frame. In addition, conversionscheduler 540.1 may switch MUX_SEL[1:0] signal 3734.4 one-half SPS clockcycle 522.1 after values for SHM 1207 control signals SELA[12:0] 3726.4,SELB[6:0] 3728.4, and DIV[1:0] 3730.4 have been switched to protectanalog to digital converter 1206 from receiving any dangerous voltagefluctuations. In response to START signal 586.1, SHM module 1207 willgenerate the actual START pulse 3768.4, as shown in FIG. 40C, to analogto digital converter 1206 to begin the conversion. Analog to digitalconverter 1206 signals the completion of the conversion to regulationcontrol module (REG) 1204 using signal DONE 3738.4.

[0324] In addition to managing the scheduling of the feedback signalsfrom the switching power supplies, conversion scheduler 540.1 may alsomanage the sampling and conversion of the external supply A and Bvoltages, and the voltages representing external and internaltemperatures. Upon request from central processing module (SYS) 1205,regulation control module (REG) 1204 schedules a conversion of theexternal and internal temperature voltages (TEMPEXT signal 3706.4 andVOUT signal 3708.4, respectively, as illustrated in FIG. 1.1.7 d).Whenthe conversion is complete regulation control module (REG) 1204 writesthe data to a status register which is read by central processing module(SYS) 1205 so that the converted temperature values may be used incouloumbmetric measurements.

[0325] Conversion scheduler 540.1 controls the conversion of feedbacksamples as well as source identification of the ADC data—i.e, whether ornot it is a voltage or current sample and to which switching powersupply it corresponds as sample data DOUT[9:0] 715.1. However, in oneembodiment, pulse widths are not adjusted if the voltage and currentsamples for a given switching power supply are within a desiredoperating range. This condition does not require VLIW engine 517.1 to docomputations, thus saving power. Thus, regulation control module (REG)1204 may include limit comparison module 560.1 to test whether or not agiven feedback signal is within the desired operating range (which maybe denoted as the deadband limits). If DOUT[9:0] 715.1 is within limits,conversion scheduler 540.1 may indicate this condition tomicrocontroller 500.1 so that no PWM adjustment calculations need beperformed for the associated switching power converter, and no DPC 1201writes are required. In addition, limit comparison module 560.1 may alsotest whether DOUT[9:0] 715.1 is within acceptable high and lowregulation limits. If DOUT[9:0] 715.1 is within these limits, limitcomparison module 560.1 directs VLIW engine 517.1 to calculate new PWMvalues as described above, and values calculated for DOUT[9:0] 715.1being within limits, are written to DPC 1201. If DOUT[9:0] 715.1 isoutside these limits, limit comparison module 560.1 directs VLIW engine517.1 to calculate new PWM values as described above, and valuescalculated for DOUT[9:0] 715.1 being outside limits, are written to DPC1201.

[0326] In response to assertion of DONE signal 3738.4, limit comparisonmodule latches in DOUT[9:0] 715.1. Although conversion scheduler 540.1and limit comparison module 560.1 are illustrated as functionallyseparate from microcontroller 500.1, these functions may be performed bymicrocontroller 500.1 or by separate state machines.

[0327] Having received sample data DOUT[9:0] 715.1 from limit conversionmodule 560.1, microcontroller 500.1 performs the pulse widthcalculations as described above. As explained in greater detail withrespect to DPC 1201, sample scheduler 510.1 schedules the correspondingpulse edges through data words DWI[19:0] 2428.4, their addressesADW[4:0] 2430.4, and control signal WE 2432.4 that will be written intomemory in DPC 1201 through a DPC interface 590.1. DPC 1201 stored datamay be read by regulation control module (REG) 1204 for testing or otherpurposes via DRO[19:0] 2442.4, address ADW[4:0] 2430.4, and controlsignal RE 2434.4 through DPC interface 590.1 As controlled by modesignal PD[1:0] 712.1 from central processing module (SYS) 1205,regulation control module (REG) 1204 may be configured to implement alow-power mode as well as the normal operation described herein. In thislow-power mode, microcontroller 500.1 and edge scheduler 510.1 arepowered down by, e.g., gating off the relevant clock signals such thatregulation control module (REG) 1204 controls only a subset of thepossible switching power converters. Regulation control module (REG)1204 subsequently passes on the PD signal to DPC 1201 and CLKGEN 1223 assignal PD_OUT[9:0], which may be delayed from the time of receipt ofPD[9:0] from central processing module (SYS) 1205 via bus 520.1. A lowpower engine 585.1 performs the necessary pulse width and samplingcalculations. For example, low power engine 585.1 may issue a conversionrequest to conversion scheduler 540.1 to receive feedback data (voltageand/or current) for a given switching power converter. To calculate therequired pulse widths based upon the received feedback information, lowpower engine 585.1 may perform a limit comparison as discussed withrespect to limit comparison module 560.1. If the sample is within adesired operating range, low power engine 585.1 may skip a number of DPCframes, e.g., four frames before again sampling feedback from theparticular switching power converter. If the sample is outside thedesired operating range, sleep engine will command DPC 1201 to changethe SFET 2404.4 and PFET 2402.4 pulse edges accordingly. To save power,the change may be based upon predetermined values stored in registers(not illustrated) associated with sleep engine 540.1 such that theimplemented PWM adjustment algorithm is a table look-up function.

[0328] In this low-power mode, CAM function in DPC 1201 is also disabledas described further herein with respect to DPC 1201 operation. Thus,low power engine 585.1 directly causes the desired pulse edge timesthrough SET[28:0] and RESET[28:0] signals 2438.4 and 2440.4. Low powerengine 585.1 may be implemented through a configured state machine orother suitable means.

x.2 LED Controller

[0329] Because switching power supply controller 1200 may be used inLED-containing devices such as PDAs, it may include LED control block,contained in central processing module (SYS) 1205 as shown in FIG. 12.FIG. 52 is a block diagram of LED control block 1214.

[0330] An interface module 30.1 receives LED control commands fromcentral processing module (SYS) 1205 (FIG. 12). In turn, interfacemodule 30.1 controls one or more LEDs using, e.g., first LED drivermodule 35.1 and a second LED driver module 40.1. Each driver module 35.1and 40.1 provides a PWM-modulated drive signal to its external LED (notillustrated).

[0331] The PWM modulation in each driver module 35.1 and 40.1 is underthe control of values written into registers within interface module30.1. The greater the pulse width specified in each PWM period, thegreater the amount of brightness shown by the corresponding LED. Inaddition, other registers within interface module 30.1 may control LEDblinking, or ramp modes wherein a selected driver module graduallychanges its PWM so that its corresponding LED gradually changes from onebrightness level to another.

X.4 Internal Power Supply Structure (GM)

[0332] Internal voltage supply (IVS) 1209 (FIG. 12) provides theoperating voltages and power for internal operations in switching powersupply controller 1200. IVS 1209 receives and provides various interfacesignals, including a reset (RSTn) signal, a power on reset (POR) signal,a clock output (CLK_OUT) signal, a clock input (CLK_IN) signal, a supplyA signal, a supply B signal, a battery 0 (batt0) signal, a battery 1(batt1) signal, and various supply or reference voltages (i.e., AVD,AVS, VDD, VSS, VDDIO[A,B], and VSSIO[A,B]).

[0333] The reset signal and the power on reset signal are received fromreset module 1215 to reinitialize or reset operations of IVS 1209, inaccordance with one embodiment, or the power on reset signal may beprovided by IVS 1209 to other circuits within switching power supplycontroller 1200, in accordance with another embodiment. The clock inputsignal is received from external circuitry and a clock output signal isprovided to external circuitry to synchronize and enable variousclocking operations.

[0334] The supply signals (supplyA and supplyB) and the battery signals(batt0 and batt1) are various external power supplies that may bereceived by IVS 1209. These external power supply sources, such as theexemplary ones listed below in Table x.4a, are coupled to switchingpower supply controller 1200 (and consequently to IVS 1209) and are usedto power up and generate internal voltages (e.g., 3.3 V) and are used aspower supplies for various circuitry, such as the core logic and tosupply or drive external power NFETs (e.g., with up to 15 V). TABLE x.4aExemplary External Power Supplies EXTERNAL POWER SUPPLY MIN V MAX VBattery 0 or 1 2 Cell NiMH 1.8 3.8 4 Cell NiMH 3.6 7.6 Lion - 1 Cell 2.74.2 Lion - 2 Cell 5.4 8.4 Supply A or B Car Adapter 9.6 14.4 plus spikesWall Adapter 4.5 15

[0335] IVS 1209 also includes a Kelvin temperature sensor (discussedbelow in reference to FIG. 54) to monitor the temperature of switchingpower supply controller 1200 or external ICs. IVS 1209 also provides avoltage reference (VREF) that is used for various circuits, such asanalog to digital converter 1206, and may also generate a power on resetsignal for distribution within switching power supply controller 1200,as explained in further detail below.

[0336]FIG. 54 is an exemplary functional diagram of IVS 1209 inaccordance with one implementation. FIG. 54 shows the four externalpower supplies 2202.4 through 2208.4 (i.e., BATT0, BATT1, SUPPLYA, andSUPPLYB, respectively) that are received via pads 2210.4 (with diodes2212.4 serving as protection devices, such as to guard against a reversepolarity condition). The BATT0, BATT1, SUPPLYA, and SUPPLYB labelsrepresent external battery source 0, external battery source 1, externalcar adapter or wall adapter source A, and external car adapter or walladapter source B, respectively.

[0337] IVS 1209 determines which of power supplies 2202.4 through 2208.4to use, if more than one is available, to generate the core voltage andthe I/O voltages for switching power supply controller 1200. Forexample, there may be two core voltages required (e.g., digital 3.3 Vand analog 3.3 V).

[0338] Switching power supply controller 1200 in accordance with oneimplementation has three modes of operation: 1) shut-down mode, 2)low-power mode, and 3) standard mode. In the shut-down mode, nothing onswitching power supply controller 1200 is powered on except whatmonitors the external sources of energy (e.g., power supplies 2202.4through 2208.4) and no current is flowing except leakage current inswitching power supply controller 1200.

[0339] In the low-power mode, internal and I/O voltages are maintained,DPCw 1201 and two external loads (i.e., regulated power supplies) areoperating, and switching power supply controller 1200 is performingcycle skipping (discussed further herein). The amount of currentrequired is generally less than in the standard mode. The low-power modeis the default mode of operation once switching power supply controller1200 is powered-up from any other mode or when neither the clocks northe registers are running or set. In the standard mode, all of switchingpower supply controller 1200 is operating and all of the external loads(e.g., seven) are being supplied with regulated power. IVS 1209 receivecommands from central processing module (SYS) 1205 which will commandIVS 1209 to the appropriate mode.

[0340] As illustrated in FIG. 54, if power is being supplied by powersupply 2202.4 or 2204.4, then this external voltage is routed to andsupplies power to a crystal oscillator 2216.4, which generates a clockfor a voltage multiplier 2214.4 (e.g., either a doubler or a tripler).Crystal oscillator 2216.4 has two pins, for input signals (XTALIN) andoutput signals (XTALOUT), via pads 2210.4.

[0341] An output of voltage multiplier 2214.4, which may be implementedusing well known circuitry, is used as an input voltage for voltageregulators 2226.4, 2228.4, and 2230.4, which supply voltages VDD, AVD,and VREF which can be of conventional circuitry. Additionally, voltageVREFH and VREFL are generated by circuits 2236 and 2238, respectively,and provided to touch screen interface 1211. As will be appreciated fromthe figures, to simplify the illustration, line have not been includedto show each connection. Instead, triangles are utilized within eachblock indicating the signal and the direction of travel of the signal.The supply voltage VDD provides an output digital core voltage (e.g.,3.3 V) and is treated as global within switching power supply controller1200. The supply voltage AVD provides an output analog core voltage(e.g., 3.3 V) and is utilized by analog blocks that require a quieterpower supply voltage than the supply voltage VDD. The supply voltageVREF shown on IVS 1209 and analog to digital converter 1206 in FIG. 12also provides an output reference voltage for analog to digitalconverter 1206. Additionally, the supply voltages VDDIOA and VDDIOB areexternal I/O power (A and B) used by internal NFET I/O buffers to drivethe external power NFET. An external capacitor (labeled generically asEXT CAP) will be generally connected to each of the corresponding bondpads (not shown). The supply voltage VDDIO3 is an external I/O powersupply (e.g., of 3.3 V) required for the general purpose I/O digitalpads.

[0342] Once the supply voltages VDD and AVD are generated, a phaselocked loop (PLL) 2218.4 operates and the supply voltages VDD and AVDare distributed. A DONEMU signal is used to cause voltage multiplier2214.4 to cease its operations. A MODE[1:0] block 2224.4 informs voltageregulators 2226.4 and 2228.4 of the proper mode of operation and isrequired for setting the appropriate current.

[0343] The input voltage to voltage regulators 2226.4 and 2228.4 is alsoprovided to power on reset (POR) block 2234.4, for resetting orreleasing switching power supply controller 1200 via a RSTN_INT signal,and also to a charge pump block 2220.4 which may be implemented by anywell known charge pump circuit. Charge pump block 2220.4 stores theamount of charge (e.g., in external capacitors) required for aninstantaneous current needed to drive the external power NFET forsetting one or two regulated power supplies. A PUMPCLK signal and aDONEIO signal are control signals that cause charge pump block 2220.4when to start and when to stop operations, respectively.

[0344] If power is being received from power supply 2206.4 or 2208.4,crystal oscillator 2216.4 and voltage multiplier 2214.4 are bypassed andthe supply voltage is routed directly to voltage regulators 2226.4through 2230.4.

[0345] A band gap reference (BGR) block 2222.4 provides referencesignals to voltage regulators 2226.4 through 2230.4 and to a Kelvintemperature sensor 2232.4. As noted above, voltage regulator 2230.4generates the supply voltage VREF. Kelvin temperature sensor 2232.4generates a VOUT signal.

[0346]FIG. 15 is a block diagram showing the interface signals of kelvintemperature sensor (KTS) 1500, which is an exemplary implementation ofKelvin temperature sensor 2232.4. Kelvin temperature sensor 1500 is anabsolute temperature sensor circuit that produces an output voltage(VOUT) linearly related to the circuit's absolute temperature. As shownin FIG. 15, Kelvin temperature sensor 1500 receives analog power andground reference voltages at terminals 1501 and 1502 and asynchronouspower-down control signal (PDN) at terminal 1503, and provides outputvoltage VOUT at terminal 1504, which is linearly related to thetemperature of the circuit between 0.0V and 3.0V.

[0347]FIG. 15A is an exemplary circuit for KTS 1500 in accordance withone implementation and highlights the basic equations that illustratehow the output voltage VOUT corresponds to temperature. For example, allof the components in FIG. 15A can be integrated on the same chip and,thus, the matching of the components can be better than 0.1%. Withoutcalibration, approximately ±5% accuracy may be obtained over thetemperature range 0° C. to 125° C. With calibration, by measuring theoutput voltage VOUT at a known temperature (e.g., 25° C.), greater than±1% accuracy may be obtained.

[0348]FIG. 54A is an exemplary interface block diagram illustratinginterface signals for IVS 1209 in accordance with another implementationand FIG. 54B is a corresponding functional block diagram. As shown inFIG. 54A and x.4c, the interface signals include a battery (BATT) signal3400.4, a switch (SWT) signal 3402.4, power supplies A and B (SUPPLYAand SUPPLYB, respectively) 3404.4 and 3406.4, respectively, an XINsignal 3408.4, an XOUT signal 3410.4, a VM1 signal 3412.4, a VM2 signal3414.4, a VM3 signal 3416.4, an IVS_CLK signal 3418.4, a DONEPUMP signal3420.4, a DONEBOOT signal 3422.4, a VOUT signal 3424.4, a RESETN signal3426.4, a VSSIOA signal 3428.4, a VSSIOB signal 3430.4, a VDDIOA signal3432.4, a VDDIOB signal 3434.4, a VREF_HALF signal 3436.4, a COLDBOOTsignal, a SWT_ADAPT a FREF signal 3438.4, a VREF signal 3440.4, an AVSsignal 3442.4, a VSS signal 3444.4, an AVD signal 3446.4, and a VDDsignal 3448.4. Some of the signals employ pads 3550.4, as shown in FIG.54A.

[0349] Battery (BATT) signal 3400.4 is the signal provided if anexternal battery is available. Switch (SWT) signal 3402.4 is used tocause switching power supply controller 1200 to go from the shutdownmode into the low power mode, or the standard mode. Power supply A3404.4 and power supply B 3406.4 are pads connected to the externalpower source (A or B, respectively). XIN signal 3408.4 is an inputsignal for a crystal oscillator 3500.4, while XOUT signal 3410.4 is anoutput signal from crystal oscillator 3500.4, both for communicationwith an external crystal oscillator (e.g., of 32.768 kHz).

[0350] VM1 signal 3412.4, VM2 signal 3414.4, and VM3 signal 3416.4 aresignals provided to and from external capacitors (labeled EXT CAP inFIG. 54B) coupled to a voltage multiplier 3504.4. IVS-CLK signal 3418.4is a clock signal from CLKGEN 1223 that is used by a charge pump 3518.4,while DONEPUMP signal 3420.4 is a signal from central processing module(SYS) 1205 to cause charge pump 3518.4 to stop. DONEBOOT signal 3422.4is a signal from central processing module (SYS) 1205 to cause a powerdetection circuit 3502.4 to stop voltage multipler 3504.4 and voltageregulators 3510.4 and 3514.4.

[0351] VOUT signal 3424.4 is an output signal from a Kelvin temperaturesensor 3516.4, which is provided to SHM 1207. RESETN signal 3426.4 is areset signal from a power on reset (POR) circuit 3512.4 and is providedto reset module 1215. VSSIOA signal 3428.4 and VSSIOB signal 3430.4 aretwo ground signals, while VDDIOA signal 3432.4 and VDDIOB signal 3434.4are two power supply signals generated in charge pump IO 3518.4, allprovided to various blocks in switching power supply controller 1200,including to NFET driver module 1202.

[0352] VREF signal 3440.4 is a reference voltage signal (e.g., 3.0 V)provided to analog to digital converter 1206, while VREF_HALF signal3436.4 is one-half the voltage level of VREF signal 3440.4, which isprovided to SHM 1207. FREF signal 3438.4 is a reference frequencyprovided by crystal oscillator 3500.4. AVS signal 3442.4 is an analogground signal, VSS signal 3444.4 is a digital ground signal, AVD signal3446.4 is an analog voltage signal (e.g., 3.3 V), and VDD signal 3448.4is a digital voltage signal (e.g., 3.3 V).

[0353] As a functional example of operation (referring to FIG. 54B), ifan external battery is supplying the power, battery signal 3400.4 willprovide a voltage (e.g., at least 1.8 V) to run power detection circuit3502.4 (which detects the voltage) and crystal Oscillator (XTAL OSC1)3500.4 to generate a clock for voltage multiplier 3504.4. Powerdetection circuit 3502.4 provides a voltage (e.g., 1.8 V) to crystaloscillator 3500.4 and detects when to exit the shutdown mode. The outputof voltage multiplier 3504.4 (e.g., twice the input voltage) is used asan input voltage for voltage regulators (VRAVD) 3514.4 and (VRVDD)3510.4, which generate a VRAVD voltage and a VRVDD voltage,respectively. A separate internal voltage doubler 3508.4 provides avoltage (e.g., 6.6 V or twice VDD signal 3448.4) to a VREF block 3506.4,which provides a stable reference voltage (i.e., VREF signal 3440.4) byemploying, for example, band gap reference circuits.

[0354] Once core logic VDD signal 3448.4 and AVD signal 3446.4 aregenerated, a phase-locked loop (PLL) circuit (not shown) along withother circuitry shown in FIG. 54B can begin operating using the voltage(e.g., 3.3 V) from VDD signal 3448.4 and/or AVD signal 3446.4. When theVRVDD voltage reaches a minimal level, a POR circuit 3512.4 exits areset state (during reset, POR circuit 3512.4 functions toasynchronously set or reset registers used in switching power supplycontroller 1200). The 8051 contained within central processing module(SYS) 1205 will then bring up the rest of the system, which enablesregulation control module (REG) 1204 to regulate an external supply(e.g., 3.3. V).

[0355] After regulation control module (REG) 1204 is regulating theexternal voltage supply (e.g., 3.3V), central processing module (SYS)1205 will assert DONEBOOT signal 3422.4. Once DONEBOOT signal 3422.4 isasserted (e.g., logical high level), IVS 1209 will turn off voltagemultiplier 3504.4 and internal voltage regulators 3510.4 and 3514.4. Thevoltage from voltage regulator 3510.4 should also go to POR block 3512.4so that the asynchronous registers (not shown) can exit their resetcondition.

[0356] Additionally, charge pump 3518.4 will receive the output ofvoltage multiplier 3504.4 and store in an external capacitor (EXT CAP)the charge needed in NFET driver module 1202 during the power-upsequence (e.g., 3 V above the power supply to drive a gate of theexternal NFET). Charge pump 3518.4 will start once IVS_CLK signal 3418.4is generated and continue pumping until DONEPUMP signal 3420.4 fromcentral processing module (SYS) 1205.

[0357] If no battery is available and an external power source isprovided by power supply A 3404.4 or power supply B 3406.4 (e.g., eithersupply providing between 4.5 V and 14.4 V), this voltage will bedetected by and run power detection circuit 3502.4 and also crystaloscillator 3500.4. VREF block 3506.4 and voltage regulators 3510.4 and3514.4 will receive as their input voltage, either power supply A 3404.4or power supply B 3406.4 to generate the analog and digital voltages(i.e., AVD signal 3446.4 and VDD signal 3448.4, respectively). Once AVDsignal 3446.4 and VDD signal 3448.4 are generated, the same procedure asdescribed above for a battery supply will take place to provide theexternal 3.3V connected back into the chip through AVD signal 3446.4 andVDD signal 3448.4.

[0358] If the chip has entered shutdown mode , and it still has powerfrom either battery 3400.4, SUPPLYA 3404.4 or SUPPLYB 3406.4, it willremain in that state with just the Xtal Osc 3500.4 and Power DetectionCircuit 3502.4 running. It will remain in this state until one of twoconditions occur: Pad SWT is pulled low or a supply is provided. Uponeither or these conditions will initiate the power up sequencesdescribed above and provide signal COLDBOOT and SWT_ADAPT to centralprocessing module (SYS) 1205.

[0359]FIG. 54C is an exemplary flowchart for a power-up sequence for IVS1209 in accordance with another implementation. Step 3600.4 begins thepower-up sequence when an external voltage is applied. If the externalvoltage is greater than a required threshold (e.g., 1.8 V) at step3602.4, then the shutdown mode is held to allow circuits to power up(step 3604.4). If the external voltage is greater than expected batteryvoltages, then the external voltage is routed to VREF block 3506.4 andvoltage regulators (LDOs) 3510.4 and 3514.4 (as discussed in referenceto FIG. 54B).

[0360] If the external voltage is around the expected battery voltages,step 3608.4 determines if a switch (SWT 3402.4) is pressed, if not thenthe shutdown mode (step 3604.4) is entered. If the power switch ispressed, step 3612.4 starts voltage multiplier 3504.4, VREF block3506.4, and voltage regulators 3510.4 and 3514.4. RESETN signal 3426.4is asserted (step 3614.4) and charge pump 3518.4 operation begins.

[0361] Step 3618.4 determines if a low battery condition exists if soIVS returns to step 3604.4. IVS remains in state 3618.4 until centralprocessing module (SYS) 1205 (referred to as 8051 in flowchart) hascompleted its coldboot operations. Once central processing module (SYS)1205 is done with these operations step 3620.4 switches off allredundant systems and the external voltage (i.e., VDD signal 3448.4) isfed back into switching power supply controller 1200. Step 3622.4 beginsoperation of voltage doubler 3508.4 and, when DONEBOOT signal 3422.4 isasserted, the standard mode or the low power mode (step 3626.4) isinitiated. When the shutdown mode command is received, step 3624.4switches off VREF block 3506.4 and voltage doubler 3508.4 and step3606.4 is repeated.

Section x.5 Converter Structure (ADC)

[0362] Referring to FIG. 12, analog to digital converter 1206 may beconstructed as a successive approximation converter (SAR) or in othersuitable architectures such a flash analog-to-digital converter. Due tothe use of sample and holds in combination with capacitor ratio basedvoltage division and multiplication; several unusual simplifications maybe made to the input of the analog-to-digital converter. A standardimplementation of a SAR converter requires an input buffer amplifier tocondition and scale the input voltage and a sample and hold circuit toprevent the input voltage from changing at the input to the SARcomparator as successive SAR DAC values are compared to the inputvoltage. In a SAR analog-to-digital converter, the conversion may becorrupted if the input voltage is allowed to change during theconversion process. The additional input stages normally required in aSAR analog-to-digital converter require that voltages to be measured bemade available and settled a significant time before the conversionstarts. This “set up time” is a particular issue in a multiplexed systemsuch as the present invention since it reduces the rate at which newinputs can be presented or demands much higher speed from theanalog-to-digital converter. Since the present invention utilizes sampleand holds at its inputs and capacitor ratio based scaling, both theinput amplifier and sample and hold sections may be eliminated from theSAR analog-to-digital converter implemented in an embodiment thuseliminating much of the set up time and several sources of error whilereducing the speed requirements and power consumption of the SARanalog-to-digital converter. The required processing speed of analog todigital converter 1206 is driven by the DPC frame rate and the number ofswitching power supplies under control by switching power supplycontroller 1200 and the desired A/D resolution. For example, ifswitching power supply controller 1200 uses a cycle rate of 524 KHz andcontrols seven switching power supplies, analog to digital converter1206 must convert 14 feedback signals plus two input signals in a DPCframe period of approximately 2 micro-seconds. If 10 bits of resolutionare desired, the resulting A/D logic clock frequency is approximately110 MHz.

x.7 Output Structure NFET (GM)

[0363]FIG. 55 is an exemplary functional diagram of NFET driver module1202 in accordance with one implementation. FIG. 55 includesinput/output (I/O) buffers 2102.4 and 2104.4, which drive correspondingexternal power MOSFETs 2112.4 and 2114.4 via pads 2106.4 and 2110.4(corresponding to UPPER_FET and LOWER_FET terminals, respectively, onNFET driver module 1202 of FIG. 12).

[0364] As shown in FIG. 55, power MOSFET 2112.4 is referred to as an“UPPER FET” and power MOSFET 2114.4 is referred to as a “LOWER FET,”with both employed to provide a regulated DC supply to a load. NFETdriver module 1202 receives via switch control bus 1303 a (i.e.,HIGHFET) and switch control bus 1303 b (i.e., LOWFET) signals shownadjacent to the bus, which contain information utilized by NFET drivermodule 1202 to control I/O buffers 2102.4 and 2104.4. A pad 2108.4 iscoupled to power MOSFETs 2112.4 and 2114.4 to provide feedback (fb) toNFET driver module 1202 regarding external load parameters (e.g.,voltage).

[0365] NFET driver module 1202 (FIG. 12) further includes interfacesignals VDDIO[A,B], VSSIO[A,B], UPFET_Source, LOWFET_Source, and IDDQ.The VDDIO[A,B] signals are supply voltages A and B, while the VSSIO[A,B]signals are corresponding A and B ground references. The UPFET_Sourceand LOWFET_Source signals monitor and provide feedback regarding powerMOSFETs 2112.4 and 2114.4, respectively, and correspond symbolically tothe feedback (fb) illustrated in FIG. 55. The IDDQ signal is providedfor test purposes.

[0366]FIG. 55A illustrates exemplary interface signals of NFET drivermodule 1202 in accordance with another implementation. The interfacesignals include a PFET[6:0] signal 3200.4, an SFET[6:0] signal 3202.4,an IDDQ signal 3204.4, a SELMODE signal 3206.4, a CNTL[1:0] signal3208.4, a VSSIOA signal 3210.4, a VSSIOB signal 3212.4, a SUPPLYB signal3214.4, a SUPPLYA signal 3216.4, an UPSENSE[6:0] signal 3218.4, aLOWFET[6:0] signal 3220.4, an UPFET[6:0] signal 3222.4, a VDDIOB signal3224.4, a VDDIOA signal 3226.4, a VSS signal 3228.4, and a VDD signal3230.4.

[0367] PFET[6:0] signal 3200.4 and SFET[6:0] signal 3202.4 are thepulses received from DPC 1201 to drive the primary and secondaryexternal NFETs, respectively. IDDQ signal 3204.4 is a test signal, whileSELMODE signal 3206.4 selects a mode of operation and CNTL[1:0] signal3208.4 provides control information.

[0368] VSSIOA signal 3210.4 and VSSIOB signal 3212.4 are return groundpaths for the external power supplies (i.e., SUPPLYA signal 3216.4 andSUPPLYB signal 3214.4, respectively). VDDIOA signal 3226.4 and VDDIOBsignal 3224.4 are high voltage sources derived from supply A 3216.4 orsupply B 3214.4, which may be controlled by DPC 1201 to regulate theload voltage as needed. VSS signal 3228.4 and VDD signal 3230.4 aredigital ground and digital supply voltage (e.g., 3.3 V), respectively.

[0369] UPFET[6:0] signal 3222.4 and LOWFET[6:0] signal 3220.4 aresignals that drive the primary and secondary external NFETs, whileUPSENSE[6:0] signal 3218.4 is a reference source voltage for the primaryexternal NFETs of switching power converters being controlled byswitching power supply controller 1200.

[0370]FIG. 55B illustrates exemplary interface signals of switch drivermodule also referred to as NFET driver module 1202 in accordance withanother implementation. NFET driver module 1202 contains I/O drivers, asexplained below, that can be used to drive external power FETs as wellas an external coil (e.g., for digital camera applications). Theinterface signals include PFET[6:0] signal 3200.4, SFET[6:0] signal3202.4, a PFET_SEL[6:0] signal 4402.4, a FET_SWAP[6:0] signal 4404.4, anEN_EXT33 signal 4406.4, IDDQ signal 3204.4, a PFETSENSE[6:0] signal4408.4, a SUPPLY_SEL[6:0] signal 4410.4, VDDIOA signal 3226.4, VSSIOAsignal 3210.4, VDDIOB signal 3224.4, VSSIOB signal 3212.4, a PADIO[6:0]signal 4418.4, a PFETDRIVE[6:0] signal 4416.4, an SFETDRIVE[6:01 signal4414.4, and an EXTDRIVE signal 4412.4.

[0371] PFET[6:0] signal 3200.4 and SFET[6:0] signal 3202.4 are thepulses received from DPC 1201 used to drive the external primary NFETsand external secondary NFETs, respectively. PFET_SEL[6:0] signal 4402.4,received from regulation control module (REG) 1204, commands whether todrive external FETs or external coils. If driving external coils, VDDIOAsignal 3226.4 or VDDIOB signal 3224.4 will be connected to the Supply Aor the Supply B. If driving external FETs, VDDIOA signal 3226.4 orVDDIOB signal 3224.4 will be boosted to voltage levels equivalent to 3 Vabove the voltage level of the Supply A or the Supply B.

[0372] FET_SWAP[6:0] signal 4404.4, received from regulation controlmodule (REG) 1204, signals NFET driver module 1202 to swap the pulsesfrom PFET[6:0] signal 3200.4 and SFET[6:0] signal 3202.4, depending uponwhether a boost or a buck is the external power topology. EN_EXT33signal 4406.4 drives EXTDRIVE signal 4412.4, which drives the externalswitch to isolate the external voltage supply (e.g., 3.3 V) from therest of the system. IDDQ signal 3204.4 is a test signal.

[0373] PFETSENSE[6:0] signal 4408.4 is the source of the primaryexternal NFET and is connected back into switching power supplycontroller 1200 to monitor the source voltage of PFETDRIVE[6:0] signal4416.4 SUPPLY_SEL[6:0] signal 4410.4 selects between the Supply A andthe Supply B for generation of VDDIOA signal 3226.4 or VDDIOB signal3224.4. VDDIOA signal 3226.4 is connected externally to PADIO[6:0]signal 4418.4 and provides a voltage level above the voltage of theSupply A (e.g., 3.0 V above) as a main power supply for PFETDRIVE[6:0]signal 4416.4 or SFETDRIVE[6:0] signal 4414.4 (if driving an externalNFET) or as a pre-driver voltage (if driving an external coil). VSSIOAsignal 3210.4 is a ground signal for VDDIOA signal 3226.4 or PADIO[6:0]signal 4418.4. Similarly, VDDIOB signal 3224.4 is connected externallyto PADIO[6:0] signal 4418.4 and provides a voltage level above thevoltage of the Supply B (e.g., 3.0 V above) as a main power supply forPFETDRIVE[6:0] signal 4416.4 or SFETDRIVE[6:0] signal 4414.4 (if drivingan external NFET) or as a pre-driver voltage (if driving an externalcoil).

[0374] VSSIOB signal 3212.4 is a ground signal for VDDIOB signal 3224.4or PADIO[6:0] signal 4418.4. PADIO[6:0] signal 4418.4 is a main sourceof input/output power for the final stage in PFETDRIVE[6:0] signal4416.4 or SFETDRIVE[6:0] signal 4414.4 and may utilize VDDIOA signal3226.4 or VDDIOB signal 3224.4 as well as the Supply A or the Supply B,depending upon the configuration (discussed further below).PFETDRIVE[6:0] signal 4416.4 drives the external primary FET.SFETDRIVE[6:0] signal 4414.4 drives the external secondary FET. EXTDRIVEsignal 4412.4 switches on or off the external FET switch used forisolating the external power supply (e.g., 3.3 V) that will be connectedback to switching power supply controller 1200.

[0375]FIG. 55C shows an exemplary functional diagram for theimplementation of FIG. 55B. In terms of general operation, two pulses,PFET signal 3200.4 and SFET signal 3202.4 are received from DPC 1201. Ifthese pulses overlap, a fail safe mode logic 4430.4 (FIG. 55D) sets theoutput signal to LOW to PFETDRIVE signal 4416.4 and SFETDRIVE signal4414.4 until the next frame. Pre-driver logic 4432.4 and 4434.4 (FIG.55D) checks for swapping between external primary and secondary outputterminals. PFET_SEL signal 4402.4 will also configure the driver eitheras driving external FETs or driving directly the external coil.PFETDRIVE signal 4416.4 needs to be, for example, 3 V higher thanPFETSENSE signal 4408.4 when driving external FETs. Hence, PFETSENSEsignal 4408.4 is connected back into the pre-driver logic to monitor thesource voltage for the external FET.

[0376] VDDIOA signal 3226.4 and VDDIOB signal 3224.4 (FIG X.7 d) areconnected external to NFET driver module 1202 and each of the channels(e.g., seven) of NFET driver module 1202 will be connected to eitherVDDIOA signal 3226.4 or VDDIOB signal 3224.4, depending on the value ofSUPPLY_SEL signal 3202.4. Each of the seven channels utilize PADIOsignal 4418.4, PFETDRIVE signal 4416.4, PFETSENSE signal 4408.4,SFETDRIVE signal 4414.4, and its corresponding VSSIOA signal 3210.4 orVSSIOB signal 3212.4. During the power-up sequence an external NFET willbe driven by EXTDRIVE signal 4412.4, which is an I/O buffer similar tothe buffers used for PFETDRIVE signal 4416.4. EN_EXT33 signal 4406.4,received from central processing module (SYS) 1205, controls EXTDRIVEsignal 4412.4.

[0377]FIG. 55D illustrates an application employing internal buffers,represented by transistors 4440.4 and 4442.4, to directly drive anexternal coil 4444.4 for the implementation of FIG. 55B. As discussedabove for this configuration, PADIO signal 4418.4 is connectedexternally (i.e., at the board level) to Supply A or the Supply B. Asshown, PFETDRIVE signal 4416.4 and SFETDRIVE signal 4414.4 may bearranged to drive in parallel external coil 4444.4 and a capacitive load4446.4, which may result in lower source impedance.

[0378] Fail safe mode logic 4430.4 verifies that PFET signal 3200.4 andSFET signal 3202.4 do not overlap. Supply_SEL 4410.4 selects VDDIOAsignal 3226.4 or VDDIOB signal 3224.4 via a multiplexer 4448.4 to routeto control logic 4432.4 and 4434.4, which control transistor pairs4440.4 and 4442.4.

[0379]FIG. 55E illustrates an application employing internal buffers,represented by transistor pairs 4440.4 and 4442.4, to drive externalFETs 4450.4 and 4452.4 for the implementation of FIG. 55B. As discussedabove for this configuration, PADIO signal 4418.4 is connectedexternally (i.e., at the board level) with VDDIOA signal 3226.4 orVDDIOB signal 3224.4. The application shown in FIG. 55E is similar toFIG. 55D and therefore will not be repeated. However, as shown in FIG.55E, external FETs 4450.4 and 4452.4 are driven by PFETDRIVE signal4416.4 and SFETDRIVE signal 4414.4, respectively, to drive external coil4444.4 and capacitive load 4446.4. When PFET 3200.4 is high, its controllogic 4432.4 maintains PFETDRIVE at a constant 3V above PFETSENSE 4408.4

[0380] Table x.7a summarizes in a truth table format the state ofvarious signals for the exemplary configurations. For PFET_SEL signal4402.4, a zero and a one indicate internal and external, respectively,For FET_SWAP signal 4404.4, a zero and a one indicate no swap and swap,respectively. TABLE x.7a PFET SFET PFET_SEL FET_SWAP PFETDRIVE SFETDRIVE0 0 0 0 0 0 (internal) (internal) 0 0 0 1 0 0 (internal) (internal) 0 01 0 0 0 (external) (external) 0 0 1 1 0 0 (external) (external) 0 1 0 00 1 (internal) (internal) 0 1 0 1 1 0 (internal) (internal) 0 1 1 0 0 1(external) (external) 0 1 1 1 1 0 (external) (external) 1 0 0 0 1 0(internal) (internal) 1 0 0 1 0 1 (internal) (internal) 1 0 1 0 1 0(external) (external) 1 0 1 1 0 1 (external) (external) 1 1 0 0 0 (fail0 (fail safe) safe) 1 1 0 1 0 (fail 0 (fail safe) safe) 1 1 1 0 0 (fail0 (fail safe) safe) 1 1 1 1 0 (fail 0 (fail safe) safe)

[0381]FIG. 55F shows an exemplary on-chip configuration block diagramfor the implementation of FIG. 55B. As shown, switching power supplycontroller 1200 receives the Supply A or the Supply B signal via pads4462.4 or through PADIO signal 4418.4, and generates VDDIOA signal3226.4 and VDDIOB signal 3224.4. Switching power supply controller 1200,through NFET driver module 1202, generates PFETDRIVE signal 4416.4 andSFETDRIVE signal 4414.4 and receives PFETSENSE 4408.4 and optionallySFETSENSE 4460.4.

x.8 Microcontroller Structure

[0382] Referring to FIG. 56, an exemplary embodiment for centralprocessing module (SYS) 1205 comprises a microprocessor core 400.1 suchas an 8051 which interfaces with external hosts through an AdvancedGeneral Purpose I/O (AGPIO) module 410.1. ADGPIO module 410.1 provides31 GPIO ports that may be individually configured to suit a hostapplication's needs, such as the ability to determine power supplystatus, an 8×8 keyboard interface, and a serial communication bus forcommunication with a host device.

[0383] Such serial communication with a host device may occur using anumber of signaling protocols as selected by a serial multiplexer 420.1.For example, serial data may be received from a universal asynchronousreceiver/transmitter (UART) 425.1, an SPI receiver/transmitter 435.1, ora JTAG receiver/transmitter 440.1. Additional serial devices could alsobe used such as Microwire, I2C, or SSI2 devices.

[0384] Microprocessor core 400.1 communicates with the serial deviceselected by serial multiplexer 420.1 on an internal bus 450.1. Adata-path multiplexer 470.1 multiplexes the data on a read data path ininternal bus 450.1 to select data from different sources such as LEDcontroller 1214 and watchdog controller 1213. In addition,microprocessor core 400.1 may receive data from and store data to thenon-volatile memory module 1216 (FIG. 12) through an external interface455.1 coupled to internal bus 450.1. As described further herein withrespect to watchdog controller 1213 and LED controller 1214,microcontroller 400.1 also interfaces with these modules throughinternal bus 450.1.

[0385] Data necessary for program execution on microprocessor core 400.1may be stored in a program memory device 460.1. Program memory device460.1 may be any technology suitable for program storage and execution,such as masked ROM, Flash memory, EEPROM, or other suitable media.Microprocessor core 400.1 may also store data in a RAM 465.1 or in anon-volatile memory module 1216 (FIG. 12). Microprocessor core 400.1communicates with other modules such as regulation control module (REG)1204 in switching power supply controller 1200 through internal bus520.1, which is also illustrated and discussed with respect toregulation control module (REG) 1204 in FIG. 12. A handshaking protocolor glue logic may be used to coordinate this communication. The outgoingdata is addressed to a particular module in a memory-mapped fashion orby SFR-mapped addresses.

[0386] Microprocessor core 400.1 is clocked by clock signal 714.1received from clock generation module 1223. However, because theregulation from DPC frame to DPC frame during normal operation is underthe control of regulation control module (REG) 1204, it would be a wasteof power to have microprocessor 400.1 clocked continuously by clock714.1 during normal operation. Thus, clock 714 is gated off duringnormal operation by the microprocessor when the microprocessor hascompleted any processing that is needed. In response to interrupts fromother modules such as watchdog controller 1213 or LED controller 1214,the power management module 480.1 allows microprocessor core 400.1 toreceive clock 714.1. Once the interrupt has been serviced, clock 714.1is once again gated off by the microprocessor core 400.1.

Section 1.2.2 Control Loops/Algorithms

[0387]FIG. 25 is a diagram of switching power supply controller 1200being used in a battery and power supply management application in, forexample, a personal digital assistant (PDA). As shown in FIG. 25,switching power supply controller 1200 (a) regulates buck converter 2570to provide a regulated DC power supply at terminal 2540, (b) regulatesDC/AC converter 2571 to provide an AC power supply between terminals2542 and 2543, (c) to charge battery 2517 through converter 2572,operating either in buck or boost mode, when an external DC supplyvoltage (e.g., 12-15 volts) is available at terminal 2544, and (d) todraw power from battery 2517, operating in boost mode, when the externalDC supply voltage at terminal 2544 is not available. In a PDAapplication, for example, switching power supply controller 1200 maycommunicate with a host processor and peripheral devices over datainterface 2573. Conventional reference oscillator circuit 2574 providesa 32.768 KHz reference clock signal for switching power supplycontroller 1200.

[0388] Even though specific converter configurations are shown in FIG.25 to illustrate the exemplary embodiments described herein, one skilledin the art would appreciate that the present invention is not solimited. Other converter configurations can be implemented within thescope of the present invention based upon this detailed description. InFIG. 25, buck converter 2570 includes inductor 2503, current-senseresistor 2504, output capacitor 2501, and MOS switches 2505 and 2506(which includes intrinsic diode 2502) receiving at their respective gateterminals the pulse-width modulated drive signals (“upper_FET_gate” and“lower_FET_gate”) from switching power supply controller 1200.

[0389] Inductor 2503, current-sense resistor 2504 and output capacitor2501 are connected in series between sense input terminal 2518 ofswitching power supply controller 1200 (one of the“upper_FET_source-sense” terminals), which is connected to the sourceterminal of MOS switch 2505, and a ground reference. Diode 2502 preventsthe voltage at sense input terminal 2518 from dropping below apredetermined voltage (e.g., approximately 1 volt) less than the groundreference. The drain terminal of MOS switch 2505 is connected to one oftwo supply terminals (“Supply A” or “Supply B”) of switching powersupply controller 1200. The drain and source terminals of MOS switch2506 are connected respectively to the sense input terminal 2518 and theground reference. The regulated output voltage is taken from theungrounded terminal 2540 of output capacitor 2501. This regulated outputvoltage is determined by the duty cycle of the pulse-width modulatedsignals received at the gate terminals of MOS switches 2505 and 2506. Inone implementation, the period of the pulse-modulated signals (alsoreferred to as a “cycle”) is two microseconds, as shown in FIG. 22.

[0390] The terminals of current-sense resistor 2504 are connected tosense input terminals 2530 and 2531 (one terminal from each of the“sense_I” and “sense_VI” buses) of switching power supply controller1200. The voltage (V_(out)−V_(IL)) across these sense input terminals isproportional to the current in inductor 2503.

[0391] External DC power can be provided to supply terminal 2508 of thesystem from terminal 2544. In converter 2572, diodes 2511, 2512 and 2513are configured to ensure that power flows only from the external powersource into the system, and to prevent the voltage at supply terminal2508 from going below a predetermined voltage (i.e., the forward biasvoltage of the diode) less than the ground reference. In converter 2572,inductor 2514, sense-resistor 2515 and capacitor 2516 are connected inseries between sense terminal 2519 of switching power supply controller1200 (one of the “upper_FET_source_sense” terminals) and a groundreference. The ungrounded terminal of capacitor 2516 is connected to thepositive terminal of battery 2517. MOS switches 2509 and 2510 receivepulse-width modulated drive signals at their gate terminals. The drainand source terminals of MOS switch 2509 are connected respectively topower supply terminal 2508 and sense terminal 2519. The drain and sourceterminals of MOS switch 2510 are connected respectively to senseterminal 2519 and the ground reference. When an external power source isconnected at terminal 2544, the pulse-width modulated drive signals atthe gate terminals of MOS switches 2509 and 2510 regulate the voltageand current for charging battery 2517. Alternatively, i.e., when anexternal power source is not connected at terminal 2544 and the systemruns from power supplied by battery 2517, the pulse-width modulatedsignals at the gate terminals of MOS switches 2509 and 2510 regulate thevoltage at power supply terminal 2508. Depending on whether the voltagesupplied by battery 2517 is higher than the desired voltage at terminal2508, converter 2572 is operated as a buck or boost converter.

[0392] The terminals of current-sense resistor 2515 are connected tosense input terminals 2535 and 2536 (one terminal from each of the“sense_I” and “sense_VI” buses) of switching power supply controller1200. The voltage (V_(out)−V_(IL)) across these sense input terminals isproportional to the current in inductor 2514.

[0393] DC/AC converter 2571 provides a high voltage AC power supply(e.g., 700 volts) for cold-cathode fluorescent lighting (CCFL) used asback-lighting in a PDA. In converter 2571, MOS switches 2521 and 2522alternatively connect inductors 2520 and 2523 to the ground reference.Inductors 2520 and 2523 are each connected between power supply terminal2508 and the drain terminal of one of MOS switches 2521 and 2522respectively. The voltages at these drain terminals controlpiezoelectric transformer 2524 to provide the requisite AC signal acrossterminals 2542 and 2543 of CCFL 2525. Terminal 2543 is connected to theground reference through sense-resistor 2526.

Section 1.2.2.1 Input Voltage/Output Current Predictive Control Loop

[0394] The terminals of current-sense resistor 2526 are connected tosense input terminals 2532 and 2533 (one terminal from each of the“sense_I” and “sense_VI” buses) terminals of switching power supplycontroller 1200. The voltage across these sense input terminals isproportional to the current in CCFL 2525. The pulse-width modulatedsignals at the gate terminals of MOS switches 2521 and 2522 regulate thepower supplied to CCFL 2525.

[0395] As can be seen from the above description, each of converters2570, 2571 and 2572 is regulated by a pair of pulse-width modulateddrive signals (one from each of “upper_FET_gate” and “lower_FET_gate”groups of signals). These signals are preferably non-overlapping (i.e.,these signals are not both at a high voltage at the same time). For eachconverter, regulation is based on a control loop receiving input signalsrepresenting the values of the controlled variables. FIG. 19 is a blockdiagram summarizing the modules in switching power supply controller1200 providing a control loop for a battery or power supply managementapplication. As shown in FIG. 19, digital to pulse converter module 1201receives from regulation control module (REG) 1204 a 10-bit value,representing the duty cycle of a pulse-width modulated drive signal andaccordingly provides one of seven pairs of pulse-width modulated drivesignals 1901 a and 1901 b. Pulse-width modulated drive signals 1901 aand 1901 b are driven by NFET driver module 1202 (not shown in FIG. 19)as the upper_FET_gate and lower_FET_gate signals from switching powersupply controller 1200. At the same time, seven pair of voltage signals1902 a and 1902 b (i.e., I[0:6], VI[0:6]), each pair representing thevoltages across the terminals of a sense-resistor, are received intosample and hold module 1207. In addition, the voltages at the twoexternal power supply terminals 1903 and 1904 (i.e., Supply A and SupplyB) are also received into sample and hold module 1207. In turn, each ofthese analog voltage signals is sampled and held for conversion byanalog to digital converter 1206, which provides regulation controlmodule (REG) 1204 a 10-bit digital value for each voltage converted.Regulation control module (REG) 1204, which implements a number ofmethods applicable to the control loop, provides digital to pulseconversion module 1201 the appropriate 10-bit value on bus 1907. Ofcourse, the number of bits to be used for each voltage converted valueis a matter of design choice depending upon, for example, the resolutionrequired in the control loop. In fact, within regulation control module(REG) 1204, computation may be carried out at a higher resolution than10-bits and residual values less than the 10-bit resolution may be keptfor multiple cycles to implement specific, higher accuracy controlmethods.

Section 1.2.2.2 Stored External Component Parameters

[0396] For each battery or power supply management application,regulation control module (REG) 1204 receives the power supply voltageV_(A) (e.g., voltage at terminal 2508), the regulated output voltageV_(out) at one terminal of the current-sense resistor (e.g., voltage atterminal 2531), and the voltage V_(IL) at the other terminal of thecurrent-sense resistor (e.g., terminal 2530). A circuit model ofconverter 2570 is provided in FIG. 57.

[0397] As shown in FIG. 57, the current I_(L) in the inductor of a buckor boost converter can be determined by the voltage drop across thecurrent-sense resistor 2504 (i.e., V_(out)−V_(IL)) divided by itsresistance R_(sense). Regulation is achieved based upon the measuredvoltage values received and quantities derivable from these receivedvalues. For example, the present invention allows regulation using aninput voltage at terminal 2508 (e.g., the power supply voltage V_(A))and an output current (e.g., current I_(L) in resistor 2504) as controlparameters.

[0398]FIG. 26 illustrates the operation of a control loop in accordancewith the present invention. As shown in FIG. 26, such a control loopincludes three phases. At the beginning of a control cycle or cycle,which is a 2 microsecond time period in one implementation, the valuesof controlled variables (e.g., output voltages) are sampled anddigitized in phase 2601. Based on these input values, parametric valuesand an appropriate response (e.g., an increase or a decrease in thevalue of a controlled variable) are computed at phase 2602. The response(e.g., an increase or a decrease in the duty cycle of the drive signalsto the MOS switches) is then applied to effectuate the changes in thecontrolled variables.

[0399] Referring back to FIG. 57, if one takes the parasitic resistancesor impedances of the converter into account, a voltage drop V_(p) can beattributed, for example, to the parasitic resistances R_(on) and R_(L),where R_(on) is the “on” resistance of one of the MOS switches (e.g.,MOS switch 2505 or 2506) and R_(L) is the parasitic series resistance inthe inductor (e.g., inductor 2503). The parasitic resistor R_(on) is notshown in FIG. 57, and the parasitic resistor R_(L) is shown as resistor5701 in FIG. 57. As discussed above, the current I_(L) in the inductorcan be obtained by (V_(out)−V_(IN)) divided by R_(ON)+R_(L).

[0400] Voltage V_(p) can be approximated using a method discussed below.In addition, a parasitic resistance R_(c) (represented by resistor 5702in FIG. 57) can be attributed to the parasitic series resistance in theoutput capacitor (e.g., output capacitor 2501). Since the actualinductance L of a commercially available coil may be more than 10%different from its nominal inductance value, and may vary significantlyover the life of the inductor, a method according to the presentinvention allows an accurate inductance value of the inductor to becalculated periodically or on power-up. The present invention alsoprovides a method, described below, for calculating the outputcapacitance C of capacitor 2501.

[0401] According to one embodiment of the present invention, regulationof the output voltage V_(out) may be carried out in the mannerillustrated in FIG. 20. The regulation method illustrated in FIG. 20recognizes that an inductor has a saturation current I_(LSAT), beyondwhich the inductor becomes resistive (i.e., the additional currentresults in energy dissipated as heat and not additional energy beingstored in the inductor). Initially, both output voltage V_(out) andinductor current I_(L) are zero. As shown in FIG. 20, the control methodof the present invention initially provides a duty cycle in thepulse-width modulated drive signals to the MOS switches (e.g., close to100%) that increases the current in the inductor at the highest rateuntil the inductor current reaches a predetermined value of thesaturation current I_(LSAT) (e.g., 95% of I_(LSAT)). During this time,the inductor current charges both the magnetic field in the inductor andthe electric field of the output capacitor (e.g., capacitor 2501), sothat the inductor current and output voltage increase along thecurrent/voltage segment 2001. When the inductor current reaches thepredetermined current value, as indicated by point 2003, the method ofthe present invention reduces the duty cycle of the pulse-widthmodulated drive signals to the MOS switches sufficiently to maintain theinductor current at that level, so that substantially all of the energytransferred by the inductor current is provided to charge the outputcapacitor. In this portion of the control method, the inductor currentand the output voltage follows current/voltage segment 2002. When theoutput voltage reaches the control target voltage V_(target), thecontrol method further reduces the duty cycle such that the energytransferred by the inductor current is substantially dissipated in theload (R_(load)) and the parasitic impedances in the converter.Regulation controls the MOS switch drive signals such that the inductorcurrent I_(L) and output voltage V_(out) follows current/voltage segment2004 to an equilibrium value within zone 2005.

[0402] In some embodiments, when the load is operating in a very lowpower mode, the duty cycle of the MOS switch drive signals necessary tomaintain output voltage V_(out) within a selected range 2005 centered atV_(target) (“controlled interval”) may fall below a minimum value. Inthat instance, regulation proceeds to an “intermittent” or “cycleskipping” mode in which a pulse may not be sent in each 2 microsecondcycle. Instead, a pulse of fixed duration is sent in the MOS switchdrive signals once every two or more cycles, such that the duty cycleaveraged over the two or more cycles achieves the duty cycle necessaryto maintain the output voltage within the controlled interval.

[0403] Subsequently, any power requirement change in a load operation(e.g., switching on backlighting), would result in a fluctuation inoutput voltage V_(out). The control method adjusts the duty cycle of theMOS switch drive signals to restore the output voltage V_(out) to theregulated voltage V_(target) along current/voltage segment 2006.

[0404] Recalling that the voltage across inductor 2503 is given by:

Ldi/dt≅LΔI/Δt≅V _(IL) −V _(in),

[0405] and because along current/voltage segment 2001 the change incurrent ΔI in inductor 2503 can be approximated by the change in voltagedrop Δ(V_(out)−V_(IL)) across sense-resistor 2504 divided by itsresistance R_(sense) over a 2 microsecond cycle (Δt), a first orderapproximation of the inductance L of inductor 2503 can be thuscalculated. Similarly, since the change in output voltage ΔV₆, over a 2microsecond frame (Δt) is given by${{\frac{V_{out}}{t} \cong \frac{\Delta \quad V_{out}}{\Delta \quad t}} = \frac{I}{C}},$

[0406] and because, along current/voltage segment 2002, the voltage drop(V_(IL)−V_(in)) across inductor 2503 is approximately zero (i.e,Ldi/dt≅LΔI/Δt≅0) and the current I is given by the voltage(V_(out)−V_(IL)) across sense-resistor 2504 divided by its resistanceR_(sense), capacitance C can also be calculated under no-loadconditions, or the combined capacitance of C and C_(LOAD). During thesame time interval, the parasitic resistance R_(L) of inductor 2503 canbe approximated from the current I_(L) and the small voltage drop(V_(IL)−V_(in)) across inductor 2503 by (V_(IL)−V_(in))/I_(L).

[0407] Other control parameters can be similarly calculated. Forexample, in a buck converter, the efficiency E at any given time isgiven by ${E = \frac{V_{out}}{V_{i\quad n}D}},$

[0408] where D is the duty cycle of the MOS switch drive at the currenttime. Efficiency E can be updated at the beginning of each cycle.

[0409] At operating point 2005, before the load is applied, the ripplevoltage at the output and the parasitic series resistance R_(C) of theoutput capacitor can be approximated using the ratio of the rippleoutput voltage divided by the average inductor current, which isdetermined by calculating a weighted average of the maximum and minimuminductor currents over a 2 microsecond cycle. The maximum and minimuminductor currents are obtained by the difference in the maximum andminimum voltage drop (V_(out)−V_(IL)) across current-sense resistor2504, sampled respectively immediately prior to MOS switch 2505 openingand closing, respectively. The weighted average of the maximum andminimum currents is calculated by weighting the maximum and minimumcurrents by the duty cycle D. In other words, as illustrated in FIG. 21:${\overset{\_}{I}}_{L} = \frac{{D\left( {V_{out} - V_{IL}} \right)}_{\max} + {\left( {1 - D} \right)\left( {V_{out} - V_{IL}} \right)_{\min}}}{2}$

[0410] The parasitic series resistance R_(C) of the output capacitor canbe approximated by the difference ΔV_(out) of the output voltage ripple,divided by the average current {overscore (I)}_(L), or${R_{C} = \frac{\Delta \quad V_{out}}{{\overset{\_}{I}}_{L}}},$

[0411] where ΔV_(out)=(V_(out max−)V_(out min)).

[0412] In the controlled interval 2005, while the inductor current isapproximately constant, the voltage drop between the input voltageV_(in) and the voltage V_(IL) 2530 at the common terminal of theinductor and the current-sense resistor 2504 represents the voltage dropacross the parasitic resistance of one of MOS switches 2505 and 2506 andthe parasitic series resistance of inductor 2503.

[0413] The efficiency loss due to switching at an MOS switch can beapproximated using data obtained from a temporary change in thepulse-modulated MOS switch drive signals. This temporary change isillustrated in FIG. 22. FIG. 22 shows a pulse-modulated MOS switch drivesignal over two intervals A and B of equal durations and equal dutycycles. (Although FIG. 22 shows interval A to be only two cycles wide,in practice, the number of cycles in each interval should be a highernumber to increase accuracy.) However, the on-portion of each cycle ininterval A is shorter than the on-portion of each cycle in interval B,so that the number of on-pulses in interval A is much higher than thecorresponding number of on-pulses in interval B for the same duty cycle.Thus, any difference in efficiencies in the converter between theseintervals can be attributed to switching losses in the MOS switches dueto each switch's parasitic impedances. Any difference ΔV_(out) in theoutput voltage is dissipated across the parasitic resistance R_(p).,which is the sum of resistance R_(on) and the resistance R_(L) ofinductor 2501. R_(p) can therefore be estimated by${R_{p} = \frac{\Delta \quad V_{out}}{\overset{\_}{I}}},$

[0414] where I is the average current over intervals A and B.

[0415]FIG. 57 also shows input filter capacitor 5705 which has aparasitic resistance R_(cin) (represented by resistor 5704), and aninput power supply (represented by battery 5706) having a parasiticresistance R_(s) (represented by resistor 5703).

Section 1.2.2.3 Absolute Value Power Supply Control Loop, IncludingUsing Control Dead Band and Variable Gain

[0416] The calculated parameter values, including the inductance, theoutput capacitance and the parasitic resistances, can be used toimplement the control methods. In the prior art, power regulation isusually provided by an adaptive feedback mechanism in which thecorrective change in pulse-width modulation is a linear function of theerror. The error is the difference between the actual and target valuesof the controlled variable which, in this instance, is the regulatedoutput voltage V_(out). Under one method, called the “PID” method, thefeedback correction is a “proportional feedback” represented by a linearsum of constant multiples of the error, a derivative of the error, andan integral of the error. In such a PID adaptive system, the systemfunction H'(s) of an adaptive system is given by:${{H^{\prime}(s)} = \frac{H(s)}{1 - {\left( {k_{1} + {k_{2}s} + \frac{k_{3}}{s}} \right){H(s)}}}},$

[0417] where k₁, k₂, k₃ are constants and

[0418] H(s) is the open-loop system function. In most systems, becausethe error is small, the feedback correction is dominated by the integralof the error, and it may take a large number of cycles to restore theregulated voltage to V_(target). According to the present invention,however, a predictive technique is used. Under a predictive technique,the amount of correction is obtained by calculating an estimatedrestorative change in the control parameters (e.g., duty cycle input)that is needed to correct the error.

[0419] A control method according to one embodiment of the presentinvention is illustrated by flow diagram 2300 of FIG. 23. As shown inFIG. 23, at step 2301, the control method examines an output voltageerror value, which is given by error=V_(out)−V_(target). If the errorvalue is less than a predetermined threshold value (“dead band”), noadjustment is deemed necessary, and the method returns to step 2300.Otherwise, i.e., if the value of error exceeds the threshold, acurrent-constrained duty cycle D_(i) is computed at step 2302.Current-constrained duty cycle D_(i) represents the duty cycle thatwould bring the inductor current I_(L) to within a predetermined offset(e.g., 0 amps) of its saturation value I_(LSAT). As explained above, thecontrol method should not drive MOS switches 2505 and 2506 beyond thisduty cycle.

[0420] Current-constrained duty cycle D_(i) satisfies the equation:${{{L\frac{I_{L}}{t}} \cong {L\quad \frac{\left( {I_{LSAT} - I_{L}} \right)}{D_{i}T}} \cong V_{L}} = \left( {V_{out} - V_{i\quad n} - V_{p}} \right)},$

[0421] where V_(L) is the voltage across inductor 2503, T is the cycleduration, and V_(p) is the total voltage drop across the parasiticresistances of inductor 2503 and MOS switch 2505 and the resistance ofcurrent-sense resistor 2504. The expression$\frac{\left( {I_{LSAT} - I_{L}} \right)}{D_{i}T}$

[0422] represents the approximate rate of change of inductor currentnecessary to bring the inductor current I_(L) to saturation currentI_(LSAT) over the time period D_(i)T (i.e., when the drive signal of MOSswitch 2505 is “on”. Solving this equation, we obtain thecurrent-constrained duty cycle D_(i):${D_{i} = {{\frac{L}{T\left( {V_{out} - V_{i\quad n} - V_{p}} \right)}\left( {I_{LSAT} - I_{L}} \right)} \cong {K\left( {I_{LSAT} - I_{L}} \right)}}},$

[0423] where we have defined K to be the value$\frac{L}{T\left( {V_{out} - V_{i\quad n} - V_{p}} \right)}.$

[0424] Observing that the product of K and inductor current I_(L)provides the duty cycle, the value of K is temporary stored and reusedwithout recomputation for calculating the voltage-based duty cycleD_(V), which is calculated next in step 2303.

[0425] Voltage-based duty cycle D_(V) is the duty cycle that isnecessary to correct for the output voltage V_(out) by the value oferror (i.e., bringing the output voltage V_(out) to the target voltageV_(target)), without regard for the increase in inductor current I_(L).For a given efficiency E, the nominal duty cycle D_(nom) necessary forproviding an output voltage of V_(target) is given by$D_{nom} = {\frac{V_{target}}{V_{i\quad n}*E}.}$

[0426] The voltage-based duty cycle D_(V) is the sum of nominal dutycycle D_(V) and an adjustment ΔD_(V) to this nominal duty cycle.

[0427] Using the equation derived above for the parasitic seriesresistance R_(C) of the output capacitor, the additional current ΔI_(L)needed to correct for the value of error is given by:${{\Delta \quad I_{L}} = {- \frac{error}{R_{C}}}},$

[0428] the incremental change ΔD_(V) in duty cycle D_(v) is given${\Delta \quad D_{V}} = {{K\quad \Delta \quad I_{L}} = {- {\frac{K*{error}}{R_{C}}.}}}$

[0429] Thus, voltage-based duty cycle D_(V) is given${{by}\quad D_{V}} = {{D_{nom} + {\Delta \quad D_{V}}} = {D_{nom} - {\frac{K*{error}}{R_{C}}.}}}$

[0430] At step 2304, the lesser one of the current-constrained dutycycle D_(i) and the voltage-based duty cycle D_(V) is selected, so thatthe resulting duty cycle does not provide a current exceeding theinductor saturation current I_(LSAT). In some embodiments, this selectedduty cycle also cannot fall below a predetermined minimum. The selectedduty cycle is then applied to the MOS switch drive signals. The drivesignals for the primary MOS switch (i.e., MOS switch 2505 connecting thepower supply voltage to the inductor) and the secondary MOS switch(e.g., MOS switch 2506) are made non-overlapping. Control method 2300returns to step 2301.

[0431] According to another embodiment of the present invention, acontrol algorithm seeking to restore the converter back to equilibriumoperation can be implemented. Equilibrium is achieved when the followingconditions are met: (a) the output voltage V_(out) of circuit targetvoltage equals the target voltage V_(target), (b) the average current{overscore (I)}_(L) in inductor 2503 equals the average current{overscore (I)}_(load) drawn by the load, and (c) no change in inductorcurrent between the DPC frames.

[0432] The algorithm uses a linear approximation of a change in inductorcurrent over a time period that is much less than the periods of thefundamental frequencies of the converter. Within a DPC frame of durationT, the primary switch (e.g., switch 2505) is “on” (closed) for aduration T_(P), and the secondary switch (e.g., switch 2506) is “on”(closed) for a duration T_(S). Thus, an incremental current ΔI_(L)results in a change in output voltage V_(out). The incremental currentΔI_(L) can be approximated by time-weighting components incrementalinductor currents ΔI_(L(P)) and ΔI_(L(S)), corresponding to the timeperiods in which the primary and the secondary switches are “on”,respectively. ΔI_(L(P)) and ΔI_(L(S)) are given by: $\begin{matrix}{{\Delta \quad I_{L{(P)}}} = {{T_{P}\left( \frac{V_{i\quad n} - {Vp} - V_{out}}{L} \right)} = {T_{P}\left( \frac{V_{i\quad n} - {I_{L}R_{pp}} - V_{out}}{L} \right)}}} \\{{\Delta \quad I_{L{(S)}}} = {{T_{S}\left( \frac{0 - {Vs} - V_{out}}{L} \right)} = {T_{S}\left( \frac{{{- I_{L}}R_{ss}} - V_{out}}{L} \right)}}}\end{matrix}$

[0433] where V_(P) and V_(S) are the voltage drops across theresistances R_(pp) and R_(ss) in the current paths during durationsT_(P) and T_(S), respectively. Referring to FIG. 57, R_(pp) and R_(ss)are given by: $\begin{matrix}{R_{pp} = {R_{sense} + R_{L} + R_{p} + \frac{R_{source}R_{cin}}{R_{source} + R_{cin}}}} \\{{R_{ss} = {R_{sense} + R_{L} + R_{s}}}\quad}\end{matrix}$

[0434] In one implementation, the sense resistor may be omitted (i.e.,R_(sense)=0). In that implementation, inductor current I_(L) is notmeasured but estimated. Because${V_{out} = {V_{C} + {\left( {I_{C} + {\Delta \quad I_{C}}} \right)R_{C}} + \frac{\Delta \quad V_{C}}{2}}},$

[0435] and${{\Delta \quad V_{C}} = \frac{I_{C}T}{C}},{\Delta \quad I_{L}}$

[0436] is given by: $\begin{matrix}{{{\Delta \quad I_{L}} = \frac{{\frac{T_{P}}{T}\left( {V_{in} - {R_{pp}I_{L}}} \right)} - {\frac{T_{S}}{T}R_{SS}I_{L}} - \left( {V_{C} + {I_{C}\left( {\frac{T}{2C} + R_{C}} \right)}} \right)}{\frac{L}{T} + R_{C}}}{{{where}\quad I_{C}} = {I_{L} - I_{load}}}} & (1)\end{matrix}$

[0437] Substituting${D\quad C} = {\frac{T_{P}}{T_{P} + T_{S}} = {{\frac{T_{P}}{T}\quad {and}\quad \left( {1 - {DC}} \right)} = {\frac{T_{S}}{T_{P} + T_{S}} = \frac{T_{S}}{T}}}}$

[0438] into equation (1) and solving for the duty cycle DC to obtain:$\begin{matrix}{{DC} = {\frac{{\Delta \quad {I_{L}\left( {\frac{L}{T} + R_{C}} \right)}} + {R_{SS}I_{L}} + V_{C} + {I_{C}\left( {\frac{T}{2C} + R_{C}} \right)}}{V_{in} + {I_{L}\left( {R_{ss} - R_{pp}} \right)}} = {\frac{{\Delta \quad {I_{L}\left( {\frac{L}{T} + R_{C}} \right)}} + {R_{SS}I_{L}} + V_{out}}{V_{in} + {I_{L}\left( {R_{ss} - R_{pp}} \right)}}.}}} & (2)\end{matrix}$

[0439] Equation (2) can be used to predict a duty cycle DC that shouldbe applied to provide a given incremental inductor current ΔI_(L). Theincremental current to be used is selected from a number of applicableincremental inductor currents (i.e., ΔI_(L)'s).

[0440]FIG. 58 is a flow chart illustrating the steps of controlalgorithm 5800, in accordance to with one embodiment of the presentinvention. As shown in FIG. 58, at step 5801, input voltage V_(in) andoutput voltage V_(out) of the power converter are sampled, and inductorcurrent I_(L) is estimated using equation (1):

I _(L)(t _(n))=I _(L)(t _(n−1))+ΔI(t _(n−1))

[0441] At step 5802, the load current load in the current DPC frame isthen calculated. The expected incremental current ΔI_(L)(t_(n)) in thepresent DPC frame charges capacitor 2501, raising its voltage V_(C) byan amount ΔV_(C). The load current I_(Load) can be estimated by:${I_{load}(t)}_{n} = {{{I_{L}\left( t_{n} \right)} + {\Delta \quad {I_{L}\left( t_{n} \right)}} - {I_{C}\left( t_{n} \right)}} = {{I_{L}\left( t_{n} \right)} + {\Delta \quad {I_{L}\left( t_{n} \right)}} - \frac{C\left( {{\Delta \quad {V_{out}\left( t_{n} \right)}} - {R_{C}\Delta \quad {I_{L}\left( t_{n} \right)}}} \right)}{T}}}$where  Δ  V_(out)(t_(n)) = V_(out)(t_(n)) − V_(out)(t_(n − 1))

[0442] (From this point forward, the parameter values are understood tobe those of the current DPC frame, and the designation t_(n) is droppedfor clarity.)

[0443] At step 5803, the voltage on output capacitor 2501 can also beestimated, at the end of the current frame, to be:

V _(C) +C _(out) +I _(C)(T/C−R _(C))

[0444] The change in capacitor voltage over the following DPC frame canalso be estimated:${\Delta \quad V_{C}} = \frac{\Delta \quad I_{C}T}{C}$

[0445] At step 5804, a number of different incremental inductor currentvalues can be calculated as candidates which corresponding duty cyclescan be used to restore the converter towards equilibrium operation. Torestore output voltage V_(out) back to target voltage V_(target) in thenext DPC frame, assuming no further change in load current I_(load), aninductor current change ΔI_(L(target)) is required:${\Delta \quad I_{L{({target})}}} = {I_{load} - I_{L} + \frac{C\left( {V_{target} - V_{C} - {\Delta \quad V_{C}}} \right)}{T}}$

[0446] However, ΔI_(L(target)) may be so large in magnitude that itrequires a physically impossible duty cycle—i.e., a duty cycle that isgreater than 100% or less than 0%. However, if a 100% duty cycle (i.e.,T=T_(p) and T_(S)=0) is to be applied in the next DPC frame, theincremental current ΔI_(L(100%)) is:${\Delta \quad I_{L{({100\quad \%})}}} = \frac{{\frac{T_{P}}{T}\left( {V_{in} - {R_{pp}I_{L}}} \right)} - \left( {V_{C} + {I_{C}\left( {\frac{T}{2C} + R_{C}} \right)}} \right)}{\frac{L}{T} + R_{C}}$

[0447] Similarly, if a 0% duty cycle (i.e., T=T_(S) and T_(P)=0) is tobe applied in the next DPC frame, the incremental current ΔI_(L(0%)) is:${\Delta \quad I_{L{({0\quad \%})}}} = \frac{{{- \frac{T_{S}}{T}}R_{SS}I_{L}} - \left( {V_{C} + {I_{C}\left( {\frac{T}{2C} + R_{C}} \right)}} \right)}{\frac{L}{T} + R_{C}}$

[0448] Incremental current ΔI_(L(O%)) is amount of inductor current thatcan be withdrawn from the converter in a DPC frame. In this instance,control algorithm 5800 computes a quantity “maximum current” ΔI_(L-MAX)that can be removed in one DPC frame to achieve I_(load)=I_(L):

ΔI _(L-MAX) =I _(load) −I _(L) ΔI _(L(O%)))

[0449] Further, at any given time, the increase in inductor current islimited by the saturation current I_(L-SAT) of the inductor:

ΔI _(L-SAT) =I _(L-SAT) −I _(L)

[0450] Thus, at step 5805, the predictive control algorithm chooses asΔI_(L) the minimum of ΔI_(L(target)), ΔI_(L(100%)), ΔI_(L-MAX) andΔI_(L-SAT). Plugging the chosen ΔI_(L) into equations 2 yields at step5806 a duty cycle between 0% and 100%, inclusive, to correct thetransient condition at the output. The duty cycle corresponding to theselected ΔI_(L) is the used at step 5807 to control the primary andsecondary switches in the next DPC frame. The selection of ΔI_(L)discussed above is valid if the system is recovering from a transientcaused by an increase in I_(load). If I_(load) is decreased a similarflow results with slight changes in the equations. In this caseΔI_(L-MAX)=I_(load)−I_(L)−ΔI_(L(100%))) and ΔI_(L-SAT)=I_(L).

[0451] The predictive control algorithm will now choose the maximum ofΔI_(L(target)), ΔI_(L(0%)), ΔI_(L-MAX) and ΔI_(L-SAT).

[0452]FIG. 59 illustrates the operation of control algorithm 5800 ofFIG. 58. In FIG. 59, the output voltage V_(out) of a power converter isshown as waveform 5901, the inductor current I_(L) is shown as waveform5902, and the duty cycle of the primary switch is shown as waveform5903. Prior to time t=0, the converter operates at 50% duty cycle, theinput voltage V_(in) is at 8 volts, and the output voltage V_(out) is at4 volts, and the load current I_(load) and the inductor current are bothzero. At time t=0, a load is connected to the output terminals of thepower converter, causing an increase of load current by 2 amperes. Atthis time, a dip in the output voltage is detected, leading to anon-zero estimate of a change in inductor current of 0.059 amperes overthe inductor current of the last DPC frame (i.e., the converter deviatesfrom equilibrium). This change in inductor current results in anestimated non-zero load current I_(load) of 1.022 amperes, and an outputcapacitor voltage V_(c) of 3.850 volts. In this instance, I_(LSAT) is 3amperes. To restore the converter back to equilibrium, control algorithm5800 estimates ΔI_(L(target)), ΔI_(L(100%)), ΔI_(L-max) and ΔI_(LSAT) tobe 5.882, 0.879, 2.630 and 2.941 amperes, respectively. Thus, at timet=2 microseconds (us), 100% duty cycle is applied (corresponding toΔI_(L(100%))=0.823). As the estimate of the load current is low, and thecorrection applied is small, the sampled output voltage V_(out)continues to drop.

[0453] At time t=2 us, the sampled output voltage dropped to 3.703volts, but the estimated inductor current I_(L) rises to0.059+0.879=0.938 amperes, the load current is estimated to be 2.378amperes, and the capacitor voltage is predicted to drop to 3.606 volts.As in the previous cycle, control algorithm 5800 selects a 100% dutycycle for a ΔI_(L(100%)) of 0.870 amperes. In the next 2 cycles (t=4, 6us), control algorithm maintains a 100% duty cycle operation to ramp theestimated inductor current I_(L) to 2.651 amperes. At this inductorcurrent, the sampled output voltage V_(out) drops to 3.505 volts, butthe inductor current I_(L) is now sufficient to prevent furtherdropping.

[0454] At time t=6 us, control algorithm 5800 estimates ΔI_(L(target)),ΔI_(L(100%)), ΔI_(L-max) and ΔI_(LSAT) to be 3.893, 0.802, 0.102, and0.349 amperes, respectively. Thus, a duty cycle of 55.03% is selectedfor the next DPC frame (i.e., time t=6 us to t=8 us). At times t=8, 10,12, and 14 us the control algorithm selects successive values ofΔI_(L-max), i.e., 0.020, 0.016, 0.017, and 0.016 amperes, respectively,corresponding to duty cycles of 51.03%, 51.79%, 52.93%, and 53.97%. Att=14 time, the sampled output voltage V_(out) climbs back to 3.728volts.

[0455] At time t=16 us, control algorithm 5800 calculates that thetarget voltage can be achieved with an incremental inductor current of−0.205 amperes, corresponding to a duty cycle of 40.76%. At time t=18us, the sampled output voltage V_(out) achieves 3.89 volts, andpredicted to achieve 4.0 volts at the end of the DPC frame. A 14.70%duty cycle is selected to maintain the output voltage V_(out) and removeinductor current to achieve the equilibrium condition that inductorcurrent {overscore (I)}_(L) equals load current {overscore (I)}_(load).At time t=22 us, the sampled voltage V_(out) achieves 4.00 volts andinductor current {overscore (I)}_(L) equals load current {overscore(I)}_(load), control algorithm 5800 selects a 52.68% duty cycle, whichapproaches the long term equilibrium duty cycle of 53.01%. The long termequilibrium duty cycle of 53.01% is achieved at time t=24 us. In oneembodiment, a “dead band” is provided in the vicinity of the targetoutput voltage V_(target) within which the voltage output V_(out) candrift uncorrected. Correction occurs when the output voltage V_(out)drifts outside of the dead band. The dead band renders the regulationless susceptible to high frequency noise.

[0456] In another embodiment, a high voltage limit and a low voltagelimit are provided on either side of the target voltage and the deadband. Should output voltage V_(out) drift outside of the dead band, butwithin the band defined by the high limit and the low limit, a fixedcorrection amount is applied without taking regulation control module(REG) 1204 out of low power mode to restore output voltage V_(out) towithin the dead band. Algorithms requiring computation, such as controlalgorithm 5800 described above, are used only when the correctionexceeds the band defined by the higher and lower limits. In this manner,power regulation can occur for a substantial amount of time under lowpower mode.

[0457] In another embodiment, the loop gain is made less than one (i.e.,only a fraction of the value of error is corrected) and varies basedupon the absolute value of error. For example, in one embodiment, forlarge output voltage excursions (e.g., error is greater than 0.5 volts),a higher loop gain is provided (e.g., 80%). For a smaller outputdeviation (e.g., less than 0.05 volts), a smaller (e.g., 20%) or zeroloop gain could be used. Variable loop gain allows a quick response tolarge changes in the power requirements at the load, but provides higherimmunity to high frequency noise for small deviations.

Section 1.2.2.4 Maximum/Minimum Bounded Control Loop

[0458] In another embodiment, a minimum duty cycle, a maximum dutycycle, or both, can be provided. The minimum or maximum duty cyclelimits the converter between a minimum power or a maximum power. In asystem in which several converters draw power from the same powersource, such as converters 2570 and 2571 shown in FIG. 25, limiting eachconverter to a maximum power prevents a large power excursion in oneconverter from interfering with the operation of another converter. Forexample, if a momentary large current is drawn from converter 2570 (FIG.25), without a maximum duty cycle limit, a voltage dip may occur atpower supply A (terminal 2508), which is also connected to converter2571. A large voltage dip in power supply A may cause a transientresponse at converter 2571. A maximum duty cycle limit may prevent suchinterference. The prescribed minimum and maximum duty cycle limits canbe stored in registers and made programmable by the users.

Section 1.2.2.5 Low Frequency Closed/High Frequency Predictive ControlLoop

[0459] As discussed above, for each cycle, sampling and digitizing inputvalues; response computation; and response application must all beaccomplished within the cycle. In one embodiment of the presentinvention, to allow an optimal response to be implemented withoutrequiring an extension to the duration of the cycle to accommodate theadditional computation required, a control method uses open-loopregulation for certain power events that are known and characterized apriori. For example, in a dynamic random access memory (DRAM) system, arefresh event—during which the storage cells of DRAM system aresystematically read—occurs in approximately regular intervals. For sucha known power event, the power requirement (“signature”) of the eventand an appropriate response can be characterized and stored in memory.When the known power event occurs and is recognized, the pre-computedresponse can be applied in the current and subsequent cycle withoutrecomputation (hence, “open-loop”). FIG. 24 and FIG. 27 illustrate alow-frequency closed loop and high-frequency open loop control method,according to one embodiment of the present invention.

[0460] As shown in FIG. 24, at step 2401, a state machine is provided tosearch for the signature of a recognized power event from the sampledinput values of controlled variables. This state machine may search fora power event signature, for example, from a table of values ofcontrolled variables stored over a moving window of several cycles. FIG.27 shows waveform 2701, which represents a signature of a power eventexhibited in the input values of a controlled variable (e.g., outputvoltage), occurring between time t₀ and time t₆. Before a signature isrecognized, the state machine selects at step 2402 a closed loop controlmethod for power regulation, such as any of the controlled loopsdiscussed above. For example, referring to FIG. 27, between cycle t₀ andcycle t₁, when the signature of the power event is recognized, theclosed loop method is used to provide the response (in this case, anincremental change in duty cycle of the MOS switch drive signals). Thus,the portion of waveform 2702 between cycle t₀ and cycle t₁—a period ofperhaps several cycles—represents the response resulting from theoperation of a closed loop control method. However, at cycle t₁, thestate machine recognizes the power event, and switches the controlmethod to the open loop control method at step 2404 for the time periodbetween cycles t₁ and t₆. The open loop method is programmed to deliverthe incremental duty cycles shown in waveform 2702 between frames t₁ andt₆, so long as the sampled values of the controlled variables during thesame period match the stored expected values. Otherwise, i.e., if theinput values of the controlled variables during operation of the openloop control method are not what are expected, the state machine revertsto the closed loop method at step 2402. In addition, as shown in FIG.24, the closed loop method can also operate in concert with the openloop method to correct any residual error value that is not corrected bythe open loop response.

[0461] A simplification of this embodiment may occur when a predictable,known power event (e.g., sounding an alarm buzzer or an excitation eventby a CCFL supply) occurs wherein the event timing is known (since it isunder program control) and the impact is known, hence appropriate powersupply response is known ahead of time. Here one does not have torecognize the signature but simply impose the appropriate response. Itcan be viewed as this same control means but with the special casewherein the time to recognize the “signature” is zero.

[0462] In one embodiment, the closed loop response integrates an errorvalue over multiple cycles and provides a corrective response only whenthe accumulated error exceeds a threshold or when a predetermined numberof elapsed number of cycles is exceeded. Alternatively, the incrementalduty cycle corrections can also be accumulated over multiple cycles andapplied only when the accumulated corrections exceed a threshold or whena predetermined number of elapsed number of cycles is exceeded. In thismanner, the closed loop method acquires immunity to high frequency noiseand provides a dampened transient response.

Section 1.2.2.6A Sequential Transient Recovery Algorithm

[0463] In one embodiment, multiple signatures can be searchedsimultaneously. To handle the case of a sequential occurrence ofmultiple transients, i.e., when a recognized power event occurs beforeanother recognized power event completes, the state machine searcheslinear super-positions of two or more power event signatures offset intime to detect such an occurrence. FIG. 28 illustrates a sequentialtransient recovery control method, in accordance with one embodiment ofthe present invention. In FIG. 28, waveforms 2801 and 2802 represent thesignatures of two power events occurring singly at times to and ti,respectively. After the occurrence of the power event of waveform 2801is detected at time t₀, the state machine also searches compositesignatures, such as waveform 2803, which is the linear super-position ofwaveforms 2801 and 2802 offset by time interval (t₁-t₀). Should thepower events of waveform 2801 and 2802 occur, the values of thecontrolled variables match one of the composite signatures. Anappropriate response corresponding to a linear super-position of thecorresponding programmed responses can be applied as an open loopcorrection.

Section 1.2.2.6 Adjacent Phase Sampling

[0464] In switching power converters, it is necessary to measure voltageand current being provided to make adjustments, if needed. In typicalprior art solutions, the entire waveform is applied to an erroramplifier and then subsequently to a comparator. The error amplifier, ifnothing were done, would faithfully amplify the output voltage ripple.This would present a rippled signal to the comparator and result inunstable or unpredictable information being used by the comparator toset the pulse width modulation. This is unacceptable, so the typicalprior art application using an error amplifier uses filtering sometimescalled compensation in the error amplifier's feedback loop, to filterout the voltage ripple, resulting in an average value being applied tothe comparator. There are at least two undesirable consequences to this.First of all, it is the average value of the ripple voltage that isregulated. Secondly, the frequency response of this error amplifier hasbeen dramatically reduced over what it might have been, reducing theperformance of the power supply.

[0465] An advantage is provided in the present invention by usingsynchronous sampling. By sampling the voltage at the same point in timerelative to the switching waveform, the switching ripple itself isremoved. More than that, it is possible to choose a point thatcorresponds to a critical parameter. A very common critical parameter inpower converter design is to maintain a minimum voltage such that thisvoltage is above the minimum requirements of the load. Microprocessorsand memories are very intolerant of voltage excursions below thisminimum point. By sampling at the voltage minimum, then, a very stablenon-rippling voltage measurement is developed over time for the voltageminimum produced by the regulator. This permits the regulator to deliverthe minimum voltage required by the microprocessor. In a prior artsolution, it is necessary to margin the regulation point to account forthe excursions above and below the average, which was derived when theerror amplifier's frequency response was compensated and the voltageripple averaged (filtered). Similarly, on current, by takingmeasurements of the current not just synchronously with a switchingwaveform to remove the current ripple effect in the measurement, butalso at a point where the current might be at a maximum and otheradvantage is achieved. The maximum current is of interest because it isneeded to prevent the coil from saturating; that is, when the currentgoes above the maximum rating for a coil, it no longer is able to act asan inductor, with its coil inductance reduced, the very small resistanceof the wire in the coil becomes the dominate parameter, and the currentcan increase rapidly, as well as creating serious noise problems interms of radiated H and E field noise from the coil and associatedcircuitry. Minimizing the maximum of peak current also minimizes theamount of noise that can come in from an external supply. Controllingthe maximum peak current can be used to regulate the rate at which apower converter turns on the ramp of its voltage. So the benefits ofsynchronously sampling voltage and current are twofold. First, theelimination of the switching noise, the ripple in the voltage and thecurrent in the measurement are removed by definition and, secondly, itallows the circuit to precisely regulate the critical portion of theparameter, rather than an average of the parameter which would result inthe circuit attempting to infer where that critical point occurs.

[0466] The switching power converter system according to the presentinvention uses sample data techniques to remove the switching noise ofeach individual switching power supply by, for example sampling theoutput voltage at an adjustable point or a fixed point immediatelybefore the rising edge of the gate drive voltage to the upper transistorin a buck converter configuration. Consider buck converter 1301.2 inFIG. 46, and refer to FIG. 42. The signal shown in the latter figure isthe gate drive signal to FET QT₁. The reference characters I and V_(o)in FIG. 42 are provided to indicate the time at which output voltageV_(o) and the current I are measured with respect to the gate drivevoltage applied to transistor QT₁. That is, V_(o) is measured beforetransistor QT₁ begins to conduct current into inductor L1. By measuringV_(o) at this time, output voltage V_(o) is at the lowest point in theswitching waveform, and therefore it has stabilized from the priorswitching cycle. By measuring the current through the inductor L1 justprior to FET QT₁ ceasing conduction, the peak current in the inductor L1is measured on each switching cycle. Similarly, the current is measuredat a point at which it has been allowed the most time to ramp towardsits final value, i.e., just before FET QT₁ turns off.

[0467] As illustrated in FIG. 42, in the successive switching cycles,the first of which extends from A to C, and the second of which extendsfrom C to E, V₀ and I are measured at the same relative position withrespect to the gate drive voltage. Points A and C in the waveformindicate the leading edge of the gate drive voltage for transistor QT₁.Although in FIG. 42 the voltage measurement time and the currentmeasurement time are illustrated as being immediately before the leadingedge and trailing edge, respectively of the gate drive voltage totransistor QT₁, other locations may be used. By measuring at the samerelative positions, ripple in the voltage and current are removed.

[0468]FIG. 42A illustrates a typical boost switching power converter. Inthis circuit, FET B.2 is turned on for a first time period and FET U.2is turned off during the first time period. The current I throughinductor L1.2 flows in the direction indicated. During a second timeperiod FET B.2 is turned off and FET U.2 is turned on, resulting in avoltage being stored in capacitor C1.1. In accordance with the presentinvention, in a boost circuit configuration such as that shown in FIG.42A, control pulses are periodically applied to the gate of FET B.2, andthe output voltage V_(o) is measured immediately before FET B.2 beginsto conduct. The current I may be measured immediately before the gatedrive signal to FET B.2 is terminated. Following the foregoing procedurewith a boost converter provides the same advantages as those pointed outabove for a buck converter. In one embodiment of the present invention,the switching cycle is 2 usec, however other cycle times may be used. Anexemplary sample time for measurement is 2 nseconds. Thus the sampletime is a very small portion of the entire cycle, which is in contrastto the prior art in which the parameter of interest is measuredcontinuously.

[0469] The operation of sample and hold circuit 1207 is described indetail in other portions hereof. Briefly, however, commands from digitalpulse control wrapper 1201 instruct the sample and hold circuit 1207when to take samples of the voltage (V₀) and the current (I). Softwarein regulation control module (REG) 1204 determines, based on themeasurements, what is needed to return the supply which is beingregulated to equilibrium. This determination may be made by acomputation, or by a look-up table. The process of returning the supplybeing regulated to equilibrium means bringing V₀ to the target voltagefor the supply; making the average current in the inductor equal to theload current; and making the change in current over the switching cyclezero. Based on the determination of what is required to bring theregulated supply to equilibrium, output signals from regulation controlmodule (REG) 1204 to digital pulse control wrapper 1201 instruct thedigital pulse control wrapper 1201 the width of the gate drive pulseswhich should be sent to both transistors.

[0470] If a single switching power converter is being controlled, theforegoing would be sufficient to remove the noise of that singleswitching power supply. That is, its own switching noise would notinfluence its voltage and current measurements being used to regulateits output voltage. In one embodiment of the present invention, thereare seven power supplies. If the gate drive signals to the switchingtransistors were applied without reference to each other, it is probablethat at some point channel-to-channel interference could occur. Forexample, if the sense lines of a first channel, which we'll call channelØ, were close to the sense lines of a second channel, which we'll callchannel 1, channel 1 might switch where channel Ø is attempting to takeits voltage measurement and corrupt that voltage measurement. If nocoordination between switching times were to be provided, because of therandom nature of where the channel 1 switching might occur, thisinterference might be for a single cycle, or several, or random infashion. In the present invention, all of the switching signals arederived internally, i.e., they're all running off of the same clock andthey are all scheduled by logic. Channel-to-channel interference isavoided by carefully scheduling the switching points of each individualphase. In the above example, were channel 1 to have its gate drivesignal applied at the time when the sample was being taken from channel0 interference could affect the measurement. In accordance with thepresent invention, the switching times are rescheduled as shown in FIG.42B. As will be appreciated by reference to FIG. 42B, by reschedulingthe gate drive signal to the transistor in CH1 to a later time, themeasurements of voltage and current in CHØ will not be affected by theswitching in CH1. Similarly, the phase of each switching waveform foreach power supply can be changed so that no phase interferes with anyother channel. In this fashion, the switching noise is removed from thesamples by sampling synchronously within each channel with its ownswitching and then across channels by scheduling the phase of eachadjacent channel. The scheduling of the gate drive waveform is performedby the edge scheduler portion of regulation control module (REG) 1204which is described above.

Section 1.2.2.7 Stored External Component Parameters

[0471] Central processing module (SYS) 1205 may be programmed by a hostwith the operating parameters of the switching power converters to becontrolled. For example, the desired voltage levels, expected powersdrawn by loads, and circuit values such as the inductance andcapacitance values of components and the operating characteristics ofthe transistors associated with the switching power supplies may all bestored in non-volatile memory. As described with respect to regulationcontrol module (REG) 1204, central processing module (SYS) 1205 may usethese external parameters to calculate an expected pulse width for eachswitching power supply prior to normal operation. Using these expectedpulse widths, central processing module (SYS) 1205 schedules thecorresponding pulse edges across a DPC cycle and provides the pulse edgeschedule to regulation control module (REG) 1204. By beginning normaloperation with this pulse edge schedule, the rescheduling of pulse edgesrequired of regulation control module (REG) 1204 during normal operationmay be reduced.

Section 1.2.2.11 Dynamic Synchronous and Non-Synchronous Operation

[0472] Referring to FIG. 29, buck converter 49 is illustrated and shouldbe referred to in connection with the following operational explanation.As illustrated in FIG. 29, a 10V input is provided and the transistorsare switched appropriately to provide a 5V output V₀. If it is desiredto provide an output voltage which is closer to the input voltage, thena current curve such as that illustrated in waveform A in FIG. 43 wouldbe seen through inductor L50. More particularly, a current I_(max) isreached during a period when FET 50 is conducting, and the current uponthe cessation of conduction FET 50 falls during the conduction of FET51, moving during the operational cycle to I_(min). This cycle isindicated in waveform A by the reference character CYCLE.

[0473] Curve A shows that current is always flowing in the inductor L50,never going to 0 hence the term continuous current is used herein todescribe this mode. FIG. 43A illustrates the voltage waveform for thecontinuous current mode at terminal S in FIG. 29. FIG. FIG. 43Aillustrates the voltage waveform resulting from parasitic effects in thedevices. It will be observed that from the I_(max) point as transistorFET 50 is switching off, that the transition time, indicated in FIG. 43Aby the dashed line area to its S low voltage state is not zero. It takesa certain amount of time for FET 50 to turn off. The amount of time isbased on the physics of FET 50 and various parasitic capacitanceeffects. Prior to the time that the voltage at terminal S istransitioning from high to low, it will be appreciated that at the highstate when FET 50 is fully on, there is I_(max) current flowing throughFET 50, but of course since FET 50 is fully on, there is no voltagedrop, therefore there is no appreciable power dissipated by FET 50. Atthe other extreme, I_(max) may still be flowing, but it's flowing at adifferent circuit because FET 51 transistor is completely switched off.Since no current is flowing through FET 50 even though there is avoltage across it, no power is dissipated, therefore the power that isbeing dissipated by FET 50 is actually occurring during the time whenFET 50 is turning off, at which point I_(max) is continuing to flow andthe voltage across transistor FET 50 is declining in more or less astraight line fashion towards its off state. Thus power is going to bedissipated in FET 50 and it's wasted because it is not delivered to theload. It will be noted that at a point after FET 50 is switched off, thevoltage waveform continues to fall below zero volts. Inductor L50 isattempting to continue to conduct at I_(max), but neither transistor FET50 nor FET 51 are on at this point, so the voltage continues to falluntil it reaches the switching threshold of diode D50, at which timediode D50 conducts and I_(max) flows through it. If nothing were done,then for the entire time that the S signal is low, current would beflowing in diode D50 with its intrinsic voltage drop. These currents canbe quite substantial (many amperes) so the power dissipated in thisexample can be considerable if allowed to continue for a significantportion of a switching cycle. For a diode voltage drop of 0.6V a currentof 2A and a duty cycle of 50% some 600 mW would be dissipated by thediode. If the power supply were designed to produce 3V at 2A then 10% ofthe power would be consumed by the diode. A synchronous rectifier, wherethe voltage drop of the diode is reduced for most of the time of eachcycle is implemented by FET 51. By reducing the voltage drop acrossdiode D50 and conducting the current at a lower voltage, less power iswasted. As illustrated in FIG. 45C, FET 51 (indicated in the figure bygate drive waveform LF) is not turned on coincident with FET 50 turningoff (indicated in the figure by gate drive waveform UF), because at sometime during that falling waveform, both field effect transistors wouldbe on, thus conducting excessive current and wasting even more powerthan we were attempting to preserve. Therefore, there is a delay, thatis FET 50 must switch completely off, the signal to its gate to turn offis asserted, then sufficient time must elapse for it to actually switchoff. Then the gate control signal to FET 51 is switched on, and then italso has a lag time in responding until FET 51 is completely switchedon. At the right hand side of the waveform in FIG. 43A, the S voltagewaveform is in the low state indicated in the figure by I_(min). At thispoint, FET 51 turns off, and again there is current in diode D50. Thiscurrent will be lower, in fact it's at the I_(min) point on the constantcurrent diagram in FIG. 43, however still enough voltage for the diodeD50 to conduct and the transistor FET 50 is turned on. This lag timeagain is necessary in order to prevent the possibility of bothtransistors being on simultaneously. When FET 50 is turned on, we havethe same situation we had at the falling edge; as the voltage across theFET 50 rises, indicating that FET 50 is turning on, there is a time atwhich current is flowing in upper FET 50, that is I_(min), when FET 50has not yet been fully turned on, and therefore power is dissipated inthat FET 50 and not delivered to the load. There is power loss thereforeat both ends of the switching cycle; however, obviously more power islost at the I_(max) point than at the I_(min) point. The foregoingrepresents a conventional waveform for a synchronous buck switchingpower supply, synchronous meaning that both FETs are turned on during atleast part of the cycle.

Discontinuous Operation

[0474] Assume that in circuit 49 of FIG. 29, our load current was forexample 2 amps, and our period was 2 microseconds. If we drew a map ofwhat the ripple would look like, we get 10 volts in and 5 volts out, sowe know the duty cycle is going to be approximately 50%. The outputvoltage being given by the approximate equation of input voltage timesduty cycle equals the output voltage, duty cycle for the FET 50. Then wewould see a waveform as shown in FIG. 30 in terms of the current ininductor L50, which goes from high 2.1 amps down to a low of 1.9 amps,yielding an average current of 2 amps. Capacitor C50 is there tointegrate this current and that is really what you see. This is the socalled “continuous mode”. In this example of continuous mode, FET 50 andFET 51 are each on for one-half of the 2 usec time period. Since theload current is greater than ½ the ripple current, current is alwaysflowing in the inductor and is never allowed to go to zero. Note thatthe current always goes in the same direction, but reverses its slope.Sometimes it's increasing, sometimes it's decreasing, but the currentnever goes to zero. Now, consider that same circuit used to supplyexactly 100 milliamps. As illustrated in FIG. 31, we would have the sameripple and the same 2 microsecond period, the current would go from ahigh+200 milliamps down to 0, with an average of 100 ma. What if we wantless? Well, there are a couple of things you could do. Let us examineone simple example, suppose we want zero. If we were to run FET 50 andFET 51 out of a phase with each other, then if we wanted 0 milliampers,and because alternately we have 5 volts supply across coil L50 when FET50 is on (10 v-5 v), and 5 volts supply across the coil when the FET 51is on (0 v -5 v), its ripple current still must be 200 milliamps so howcan you get 0? Well, you get 0 because the ripple would look like thatillustrated in FIG. 32. There is −100 ma at time 0 and at 2 usec. Then+100 ma at 1 usec resulting in the current delivered to the load is 0.In order for the current to be negative in inductor L50, it means thatat the points where the current crosses the time axis, the currentactually reversed direction in inductor L50. FET 51 is on for exampleduring this phase and inductor L50 was completely discharged, thencharged in the opposite direction. Now, the current flows in the otherdirection, the negative direction. It's flowing out of the load insteadof into the load. When we turn off FET 51, inductor L50 flies positive.Current flows first through the intrinsic diode in FET 50 and the nowclosed FET 50 closes, actually sending energy back into the power supplyfrom before, and around and around it goes. This is a really poor way tomake 0 milliamps because 200 milliamps are being shipped through all ofthe parasitic losses in the circuit two ways to make no current. Theright answer for making no current is not to do anything, leave bothFETs off. Discontinuous mode, which is illustrated in FIG. 33, is moreefficient at low currents. Using the same duty cycle, and slope, we turnoff FET 50 and turn on FET 51 when the current gets to . . . forexample, 100 milliamps, which is 25% of the cycle time, then the currentramps down to 0 by 50% of the cycle time. This means an average of 50 mAof current was flowing for the first 50% of the cycle. During the secondhalf of the cycle, 0 mA is flowing in the coil and with both FETs offzero volts are across the inductor and 0 mA continues to flow for thesecond 50% of the cycle. Considering these percentages, what results is25 mA over the full 2 microseconds, the total switching cycle in ourexample. The current was not continuously flowing in inductor L50, hencethe term discontinuous current. Between 50% and 100% of the 2 usec timeperiod both FET 50 and FET 51 are turned off.

[0475] If we need to reduce this current still further, then the pulsesdriving the gates of FET 50 and FET 51 would be made shorter and shorteruntil at some point because of the dynamic that turns the transistors onand off, the pulse required would become so short that it would beimpractical to make. In other words, the time of the pulse would beentirely consumed by the rise and fall time of the FET. In thiscondition, you actually put a pulse out and wait a number of cycles andthen put another pulse out. This is called cycle skipping which is justa more extreme case of the discontinuous mode of operation. Cycleskipping is illustrated in waveform C of FIG. 43.

[0476] As an example of how much of a problem this is, consider powersupplies of the present invention which are designed to provide thestandby power for a PDA which is asleep. The current consumed by theSDRAMS in the PDA when it's asleep is on the order of 2 ma. With a 10 uffilter capacitor such as C50, it would take 150 microseconds for thevoltage to decay the 30 millivolts that may be typically used in thedead band of a control loop. That is 75, 2 usec cycles skipped betweeneach pulse used to drive the FETs. For some power supplies in this modeonly 150 uA may be consumed. Under these conditions many seconds mayelapse between individual pulses.

[0477] In continuous current mode the steady state duty cycle changes avery limited amount as the current is changed. Once the current fallsbelow ½ the ripple current, the desire to maintain efficiency suggeststhat the current be allowed to become discontinuous. In discontinuousmode, the current delivered is scaled by the amount of time both FETsare off and therefore the timing of the pulses delivered to the FETsmust change rapidly with current. A different regulation algorithm maybe used depending on which mode is required by the load current. Modechanges can represent a significant challenge in prior artimplementations based on analog comparators and amplifiers. On a digitalbasis, the circuitry of the present invention, can detect that the loadcurrent is less than ½ our calculated ripple and simply solve for thecorrect FET timing based on discontinuous mode. This change effects onlythe calculation but has no effect on the structures utilized for theoutput drivers, the A to Ds, or the sample and hold circuitry.Accordingly, during the discontinuous operation, we don't have theinductor feeding current back to our supply. So we avoid the so-callednegative current, negative current meaning the current flowing from thecoil back out to the power supply. In discontinuous mode, a majorobjective is to prevent the current in the coil from becoming negative.In this example the output voltage is ½ the input voltage implying thatFET51 would need to be on for exactly the same length of time as FET50.There is more subtlety than this because of the intrinsic diode D50,which exists across FET 51 from terminal “S”, which is the point wherethe inductor L50 intersects FETs 50 and 51. The purpose of thesynchronous transistor FET 51 is to reduce the voltage drop across theFET when there is current flowing. There is a hazard in waiting too longto turn off FET 51 because this would cause the current in the diode tobe reversed creating a large ringing waveform at terminal S when FET 51eventually opens. This ringing is undesirable because of theinterference it produces as well as a small negative impact onefficiency. One way to mitigate this potential problem is to turn FET 51off slightly before the point at which the current in inductor L50 wouldcross 0 current. Since the current is quite low at this point, there isvery little penalty in terms of power In our implementation, we utilizealgorithms in regulation control module (REG) 1204 to control theconduction/non-conduction of the FETs. In the prior art, the current inthe inductor is measured continuously and an attempt is made to detectthe instant where the current in the inductor crosses 0, and thenrelease the drive to the inductor. A problem that is encountered is thatthe zero current point is often detected late because there is apropagation delay time in the comparator and on the switchingtransistor. In an attempt to solve this problem, “a ring killer circuit”may be used, which is another transistor placed across the inductor,after the lower transistor is off, the transistor is turned on acrossthe coil to discharge it.

[0478] Reference to FIG. 43B and FIG. 43C in connection with thefollowing description illustrates that the synchronous mode of operationis not desirable in some load situations. First consider FIG. 43B whichshows a very long duty cycle, that is the time that the S signal is low(indicated by A in the figure) is very short. This can occur when theinput voltage is very close to the output voltage. Coincidentally, thisis also a time when switching power supplies may be their most efficientat least in the buck converter configuration. If we assume, for example,that time A is equal to 100 ns, there is not sufficient time to turn onFET 51, and if one tried to do that, it would have to be turned offalmost immediately risking an overlap with the conduction of FET 50.Thus for a very long duty cycle, that is FET 50 conducting for a highpercentage of the total cycle, it is not desirable to use FET 51. Thislimitation will typically define the maximum duty cycle that asynchronous buck switching power supply can attain, that is it canattain a duty cycle that is so long that there is insufficient time toturn FET 51 on and off. In accordance with one aspect of the presentinvention, the duty cycle of FET 50 is monitored by regulation controlmodule (REG) 1204, and if the duty cycle is sufficiently long, thendynamically the system is configured such that no gate drive signal isapplied to FET 51 so that is never conducts. This dynamic operation isdescribed fully below.

[0479]FIG. 43C illustrates a plot of the voltage at S as a function oftime in a mode of operation that is the other extreme of operation, thatis at extremely low load currents. The S waveform of this figurecorresponds to the discontinuous current mode such as that illustratedin waveform B of FIG. 43. The initial voltage at terminal S is betweenthe input voltage V_(in) and ground, that is the initial voltage wouldbe at the output voltage V₀; that is if the current in inductor L50 iszero, then the voltage across inductor L50 must also be zero. From FIG.43C, it will be noted that transistor FET 50 is switching on beforegenerating a short on pulse. The duty cycle of FET 50 is indicated inFIG. 43C and it will be appreciated that FET 50 is on for a very shorttime. When FET 50 is off, inductor L50 forces the S term down to groundand then below ground, in which case diode D50 conducts as before. Thenthe current in diode D50 decays as the very small amount of current ininductor L50 decays until eventually the current in inductor L50 is nolonger sufficient for diode D50 to conduct. The voltage on inductor L50rises against the various parasitics, that is the voltage at terminal Srises against the various parasitic capacitances in the circuit untilagain it reaches the output voltage V₀ where it remains until the nextpulse is delivered, that is when FET 50 is turned on at the beginning ofthe next cycle. In this mode, it is not advisable to use FET 51, notbecause of insufficient switching time to turn FET 51 on, but becausethere is insufficient current to sustain inductor L50 below ground forlong enough for FET 51 to be turned on. An attempt to turn FET 51 onwould likely result in it being on too long, and the current in inductorL50 would actually reverse direction, that is flow from the load toground, resulting in a ring effect when FET 51 is turned off. Thus inthis mode, to avoid the inefficiency resulting from current flowing outof the load, and also the interference caused by this ring effect, it isdesirable to operate in a non-synchronous mode in which FET 51 would notbe turned on during an operational cycle. Thus for extremely short dutycycles, the system dynamically changes from synchronous tonon-synchronous operation based on the duty cycle of FET 50 fallingbelow a predetermined minimum value. It should also be noted that forlonger duty cycles in a discontinuous current mode, FET 51 should beturned on for a part of the cycle, but not the entire cycle. Theabove-described discontinuous current in waveform C in FIG. 43 forterminal S is one that would be typical of what would be seen in cycleskipping. In the case of discontinuous current where a pulse isgenerated on every cycle as shown in waveform B of FIG. 43, there may bea time long enough that the FET 51 could be turned on for a time whichis calculated to be less than the time required to discharge inductorL50, and then FET 51 would be turned off so the inductor L50 cancomplete its discharge through diode D50, which would automatically turnoff when its current became zero thus avoiding the ring effect.

[0480] Switching power supply controller 1200 calculates when a powersupply circuit such as circuit 49 should be changed from a synchronousto nonsynchronous mode based on a number of factors. For example, assumethat FET50 is required to be on for a relatively long portion of thecycle time in order to produce V₀ having a magnitude near the magnitudeof V_(in). In one mode of operation, the manufacturer's operationalcharacteristics of FET51 are stored in nonvolatile memory 1216. ofparticular relevance to this operation is the turn-on/turn-off time forFET51. As noted above, if the portion of the duty cycle that FET50 mustbe on is relatively large, then the time available to turn FET51 on andthen off before the next cycle may not be sufficient. Regulation controlmodule (REG) 1204 in conjunction with system hardware central processingmodule (SYS) 1205 perform a computation, based on the pulse width neededto drive FET50 and the remaining time in a cycle for a pulse to turnFET51 on and then off, of whether a gate pulse should be generated toturn FET51 on and then off during the remaining portion of a cycle. Inaddition to the required on-off transition time of FET51, thepropagation delay in driving the gate of FET51 is also considered in thecomputation. If the time remaining in a cycle is insufficient to turnFET51 on and off, then regulation control module (REG) 1204 does notsend a command to digital pulse control wrapper 1201 to generate a drivepulse to the gate of FET51, thus providing dynamic change fromsynchronous to nonsynchronous operation of the power supply beingregulated by switching power supply controller 1200. In an alternatemode of determining whether FET51 should be turned on at all in a cycle,switching power supply controller 1200 examines the power lossconsideration. Even if the time remaining in a cycle is sufficient toturn FET51 on and off before the beginning of the next cycle, from apower loss standpoint it may be preferable not to do so. For example, ifthe system calculates based on the current flowing in inductor L50 thatthe power consumed by the conduction of FET51 will be greater than thepower that would be consumed by intrinsic diode D50, then no gate driveis applied to FET51 and the regulated power supply is operated in thenonsynchronous mode.

[0481] At the other extreme, where FET50 needs to be on for a relativelyshort portion of an operational cycle, then it may not be appropriate toturn FET51 on. The system calculates, based on the current throughinductor L50, the amount of time it would take for the current in L50 todrop to zero after FET50 is turned off. This computation is possiblebecause the characteristics of FET51 and the other components of supply49 are stored in NVM1216. If the computed time for the current to fallto zero is less than the time it would take to turn FET51 on and off, itis preferable not to utilize FET51. Instead, the current is permitted todecay to zero through intrinsic diode D50. In an alternative mode, thepower consumption can be computed to determine the advisability ofturning FET51 on and off. Based on the results of a comparison of powerconsumed if FET51 is used and letting the current decay through diodeD50, the system determines if the operation should be synchronous ornonsynchronous.

[0482] The above analysis considers the synchronous versusnonsynchronous operation of a buck circuit. Similar analysis of theoperation and the decision to operate it in a synchronous ornonsynchronous mode is made by switching power supply controller 1200for a boost circuit or SEPIC. Consider the circuit shown in FIG. 46, andassume that QT_(Ø), QB_(Ø), LØ, RØ and CØ are being controlled as aboost circuit by switching power supply controller 1200.

[0483] Further assume that the Batt. Ø has an output voltage which isslightly below that needed for Supply A. Switching power supplycontroller 1200, based on the voltage of Supply A, sensed over lead F1,and the battery voltage sensed over lead S2, configures the circuit to aboost configuration based on the sequence of gate drive pulses to thegates of QT_(Ø) and QB_(Ø). Because the difference between the batteryvoltage and the required voltage of Supply A is small, the gate pulseprovided to QB_(Ø) will have a relatively short duration. If the circuitwere to be operated in a synchronous mode, after QB_(Ø). was turned off,QT_(Ø).would be turned on to deliver current, and hence power, to chargecapacitor C_(E) to the slightly higher voltage required. The magnitudeof the current through RØ is computed by switching power supplycontroller 1200 since the resistance of RØ is known to the system,having been prestored in nonvolatile memory 1216. Similarly, thecharacteristics of the transistors are also prestored in non-volatilememory 1216. Knowing the foregoing parameters, switching power supplycontroller 1200 computes and compares the power losses for the scenarios(i) in which QT_(Ø) is turned on and (ii) where QT_(Ø) is not turned on.As will be recognized by those skilled in the art, even if QT_(Ø) is notturned on, current will flow through it because of the intrinsic diode(not shown) of QT_(Ø). If the result of this computation and comparisonshows that less power will be consumed by not turning on QT_(Ø), thenswitching power supply controller 1200 will not provide a gate pulse toQT_(Ø), resulting in nonsynchronous operation. It will, of course, beappreciated from the above that the decision to operate eithersynchronously or nonsynchronously is made dynamically by the system,unlike the prior art in which typically the user sets the circuit tomode of operation to one or the other, and any change must be mademanually by the user.

[0484] It will be appreciated that in above we have described anarchitecture where a synchronous rectifier is used in a switching powersupply only for the operating regimes where it improves efficiency,while in other regimes of very long and very short duty cycles, thesynchronous switching feature is dynamically eliminated to avoidinefficiency.

Section 1.2.2.12 Digital Resonance Control Loop

[0485]FIG. 44 illustrates a half-bridge high voltage power supplycircuit, indicated by reference character 1.2.2.12, which can be used topower a cold cathode fluorescent light bulb CCFL1. In a half-bridgearchitecture, energy is applied first to one side, then to the other.Inductors L12 and L13 replace the upper two transistors that what wouldcomprise a full bridge. Half-bridge circuit 1.2.2.12 illustrated in theabove-named figure includes in a first leg inductor L13 which isconnected in series with FET A between a 5V supply and ground.Similarly, in the second leg, inductor L12 is connected in series withFET B between the 5V supply and ground. The gates of FET A and FET B aredriven, for example, with waveforms WF1 and WF2 respectively or WF3 andWF4 are respectively shown in FIG. 44A. The drive control signals forthe gates of these transistors are provided, for example, by NFETdrivers module 1202 illustrated in FIG. 12. Feedback signals from senseresistor R12 are provided over lines C1 and CØ to the sample and holdmodule 1207 also illustrated in FIG. 12. The duty cycle of gate drivesignals are adjusted as a function of the changes required to provide anappropriate voltage for CCFL1. Piezoelectric transformer PZT1 may beimplemented, for example using a transformer KPN 6003A from CTS WirelessComponents located at 4800 Alameda Blvd., NE Albuquerque, N. Mex.Similar devices may be, of course, substituted. As illustrated in FIG.44, the input to terminal T1 of PZT1 is provided from the commonconnection between inductor L13 and the drain of FET A, and the input toterminal T2 is provided by the common connection between inductor L12and the drain of FET B. The output of piezoelectric transformer PZT1 iscoupled to one side of CCFL1. The other terminal of CCFL1 is connectedto the upper terminal of sense resistor R12, the lower terminal of whichis coupled to ground.

[0486] Although circuit 1.2.2.12 is driving a piezoelectric transformer,it could be used to drive a conventional magnetic transformer.Piezoelectric transformers differ from magnetic transformers in that themethod of converting from a lower voltage to a higher one, with aproportionate decrease in current, is electromechanical in nature, butotherwise they have similar characteristics, that is, they come involtage in to voltage out ratios. In one embodiment of the presentinvention, PZT1 has a mechanical advantage of 100 to 1. This means thatfor every volt impressed across the input terminals T1/T2, 100 voltswould be provided at output terminal OT. Piezoelectric transformers,since they are electromechanical in nature, have a natural resonantfrequency and they will not tend to operate outside of a relativelynarrow band of frequencies that are determined by the mechanicalcharacteristics of the device. This frequency can vary from device todevice. That is, it's not completely process controlled in themanufacture, and although the device specification provides a value forthe expected resonant frequency, the actual resonant frequency can varymany percentage points one way or the other. The optimal efficiency isobtained at the resonant frequency and operation far enough away fromthe resonant frequency will actually cause the device to fail tooscillate. FIG. 44A shows several examples of driving waveforms.Waveforms WF1 and WF2 are applied to the gates of transistors FET A andFET B, respectively. These waveforms show the maximum drive amplitudethat would be possible which would be each of these waveforms at 50%duty cycle, 180° out-of-phase. A cycle for WF1 is indicated in FIG. 44A.A cycle for WF2 is the same length of time; however the start time isoffset. This would result in a driving waveform of approximately 5 voltsto piezoelectric transformer PZT1 and when operated within resonance,this would result in approximately 500 volts AC being applied to CCFL1.As will be appreciated by reference to FIG. 44A, waveforms WF3, WF4 havethe same frequency as waveforms WF1 and WF2, however they have shorterduty cycles. Applying these shorter duty cycles reduces the energydelivered to PZT1 and correspondingly provides essentially a function ofcontrolling the voltage and current output of the piezoelectrictransformer. With this circuit, it is important to discover the resonantfrequency of PZT1 and remain on the resonant frequency. Severalalgorithms are possible. One example of a resonance algorithm is tochange the frequency of the drive signals to terminals T1 and T2 whileobserving the feedback signals C1 and CØ. At frequencies which are faraway from the resonant frequency, there would be no feedback seen, as novoltage should be applied across the CCFL1. Starting from a frequencybelow the minimum listed by the manufacturer of PZT1, as the frequencyof the input drives to the gates of FET A and FET B is increased, CCFL1will begin to ignite, and a signal will be detected at C1, CØ. As thefrequency is increased, the phase relationship between the signal C1, CØand signals WF1, WF2 will begin to shift, and resonance is indicated atthe point where a 90° phase shift is observed. A second way to determinewhen the resonant frequency of PZT1 has been reached is to examine theamplitude of the signal at C1, CØ, knowing that PZT1 has a maximumoutput at its resonant frequency. The frequency of the gate drivesignals is swept until a voltage appears at CØ, C1 indicating that thecurrent is flowing through CCFL1, and then the frequency can be furtherramped and the voltage at C1, CØ monitored until a peak is arrived at,again indicating resonant operation. It should be noted that thetopology could be supported in combination with the other topologiessuch as buck, boost, and SEPIC. When using synchronous sampling, alsosometimes referred to herein as adjacent phase sampling, as thefrequency of drive signals WF1, WF2 is changed, scheduling electronicsin regulation control module (REG) 1204 may need to vary the edgesslightly for WF1, WF2, so that the voltage and current samples beingtaken for the other supplies being controlled by switching power supplycontroller 1200 are not corrupted, and such that the samples taken fromCØ, C1 on this supply will not be corrupted by the gate drive signalsfor the other supplies.

Section 1.2.2.13 Linear or Fold Back Current Limiting from the SameStructure

[0487] Power supplies can be designed to regulate voltage, current orpower. Constant voltage power supplies are used for things likemicroprocessors and memory devices and other voltage operated devices.In the case of a power supply which is designed to regulate voltage, thepower supply may have a maximum current which is specified for safety orfor noise reasons or other reasons and the power supply will regulate involtage until such time as the current exceeds a preset limit. Thislimit is typically set by external components like resistors or similarcomponents. At that point, a fault condition exists in the power supplyand the power supply will go back to a very low current. This techniqueis known as fold back current limiting. This provides protection in thecase of a short circuit condition presented to the power supply, byhaving the power supply limit the maximum current to a very small numberso that neither the power supply nor whatever element that caused thetemporary short circuit would be damaged. The power supply in the foldback mode does not regulate the current, but rather limits it to a verysmall number, and its main operational mode is in voltage. An alternateapplication for a power supply is in constant current. Constant currentpower supplies power devices that rely on current for their function, anexample of this kind of a device being an LED (light emitting diode)which produces light in proportion to the amount of current that isflowing in it. The voltage applied to the LED is not particularlyimportant and in fact it varies depending on temperature and otherfactors, but the current will always produce a similar proportionalamount of light fairly independently of other parameters. A constantcurrent power supply does not examine the voltage in its control loop;it examines the current and attempts to regulate the current through theload to be a constant number, essentially supplying whatever voltage isnecessary to maintain that constant current. It can be seen from thisthat a constant voltage power supply with fold back current limiting hasa control loop which regulates the voltage and watches the voltage,treats an over-current condition as a fault and then takes protectiveaction to make the current very small until the short is removed and thevoltage is allowed to rise. A constant current power supply regulatesthe current and a fault condition for a constant current supply can bethat the voltage has risen to too high a level, thus indicatingtypically that the load has open circuited. In one implementation of theinvention, all of the feedback terms, current and voltage are derivedfrom analog to digital converter analog to digital converter 1206 (FIG.12). Thus the feedback is turned into numbers at this point before anycontrol is attempted to be applied. Similarly the control output pulsewidth modulated signals are also digitally controlled. In between theseis a processing element in regulation control module (REG) 1204, whichcan run a variety of algorithms for any channel controlling a powersupply. The algorithms can, for example, regulate voltage producing aconstant voltage power supply with fold back current limitingcharacteristics for error, or regulate for constant current whereexcessive voltage would be a fault, all without altering the samplingstructures such as sample and hold SHM 1207 (FIG. 12), analog to digitalconverter 1206 (FIG. 12), or the DPC 1201 (FIG. 12). An example of anapplication for this general purpose capability is in battery charging.For a battery using lithium ion chemistry, a constant current should beprovided for the first part of the charge cycle, and then a constantvoltage should be applied until the current has fallen below a minimumlevel. In this operation, the same power supply circuit can becontrolled by switching power supply controller 1200 (FIG. 12) and theoperational control mode for the power supply circuit changed fromconstant current to constant voltage. The hardware for implementing theforegoing includes regulation control module (REG) 1204, the SHM 1207,analog to digital converter 1206, and DPC 1201. This hardware and thecontrol loops are described in other portions of the application.

Section 1.3 Converter Topology/Topology Equivalents Supported Section1.3.1 Buck, Boost, Sepic, Sync, Half-Bridge, Multi-Phase etc. from aSingle Controller Structure

[0488] The buck converter illustrated in FIG. 45 derives its outputvoltage, neglecting parasitic effects, by the following straight forwardequation:

V _(o) =V _(in) −DC _(UB)

[0489] Where:

[0490] V_(o) is the output voltage

[0491] V_(in) is the input voltage, and

[0492] DC_(UB) is the duty cycle of transistor UB

[0493] In the above equation, duty cycle (DC) is the percentage of thetotal cycle that transistor UB is on expressed as a decimal number. Forexample, if the duty cycle (DC) is 50%, then V_(o) is one-half ofV_(in). FIG. 45A illustrates the current I and output voltage V_(o) as afunction of the conduction of transistors UB and LB in FIG. 45. As willbe noted in that figure, the voltage and current cycle is indicated byCycle in the figure and spans the time elapsed between the leading edgesof the gate drive signal to transistor UB. This means that there's adirect proportional relationship between the duty cycle in the upper FET(UB) with the output voltage and the duty cycle is the proportion ofinput voltage to output voltage. So this means that if the outputvoltage were to fall below a preset value that a small increase in dutycycle could correct the error. If the voltage were to be higher than itshould be, then a small reduction in duty cycle would put the voltageback where it was supposed to be.

[0494]FIG. 45B illustrates boost supply 1.3.1B. In the boost supply, theaction is quite different. More particularly, as pointed out above,power is sent to the inductor L1.3 by transistor UB in the buck supplyof FIG. 45. In contrast, in the boost supply illustrated in FIG. 45B,the conduction of transistor LF energizes the inductor L1.3B. Referringto the timing diagrams in FIG. 45C, it will be appreciated that thecurrent ramp in inductor L1.3B is started by the transistor LF, where asin the buck converter of FIG. 45, the current ramp is started by theupper transistor UB. The output voltage V_(o) may be expressed by thefollowing formula: ${V_{o} = {V_{in} \cdot \frac{1}{1 - {DC}_{LF}}}},$

[0495] Where DC_(LF) is the duty cycle of transistor LF.

[0496] In the buck converter of FIG. 45, a fifty percent duty cycleresults in an output voltage V_(o) that's one half the input voltageV_(in). In the boost converter of FIG. 45B, a fifty percent duty cycleresults in an output voltage V_(o) that is twice the input voltageV_(in). In addition, as the duty cycle of transistor LF increases, theoutput voltage V_(o) increases for the boost supply. For the bucksupply, as the duty cycle of transistor UB increases, the output voltageV_(o) increases. So it will be seen from the above that if one were toconstruct a feedback loop for the buck supply, wherein a change in theoutput voltage would result in a proportional change in the oppositedirection for transistor UB, if one then took that same feedback networkand applied it to the boost supply, the control would be reversed. Thatis, for the boost circuit (FIG. 45B), an increase in the output voltageis desired, and the duty cycle of UF was increased, thereby reducing theduty cycle of transistor LF, output voltage V_(o) would actually go thewrong way, so the control loop would have to be reversed. In addition tothat, if one were to attempt to use the absolute values of the dutycycles, that would not work because of the inverse proportionality inthe case of the boost supply, so it should be clear that these twoswitching power supplies need a reversed sense of feedback and they needdifferent feedback mechanisms and a different sequence of control. As anexample, in the buck converter, it will be noted from FIG. 45A thattransistor LB turns off before transistor UB turns on during a powercycle. But in the boost circuit (FIG. 45B), the transistor LF turns onafter transistor UF turns off in a power cycle. So, again, the sequenceof events, which signal provides the power, which signal is the leadingsignal, is actually reversed.

[0497] Switching power supply controller 1200 (FIG. 12) is adapted toalso control what is referred to in the art as a single-endedprimary-inductance-converter (SEPIC) circuit. A typical SEPIC circuit isillustrated in FIG. 46, and indicated by reference character 1301.3. Inthis circuit, Batt. 3.3, which provides Supply B voltage, drives one endof the primary (indicated by reference character P) of transformer T3.3.The other end of the primary is connected to FET 3.3. Input capacitorC3.4 is connected across Batt. 3.3. Capacitor C3.3 is connected betweenone terminal of FET 3.3 and one terminal of the secondary (indicated byreference character S) at transformer T3.3 as well as to one terminal atFET 3.4. Transistor FET 3.4 is coupled between one terminal of thesecondary S and one terminal of sense resistor R3.3, the other terminalof which provides V_(out). Although intrinsic diodes are onlyillustrated across FETs QB₁, 3.4 and 3.3, they are inherent in all ofthe field effect transistors. Capacitor C3.4 is connected between theV_(out) terminal and the common ground for the circuit. Feedbacks toswitching power supply controller 1200 are provided over lines S6, S7,S8 and S9. The gate drive signals to FET 3.3 and FET 3.4 are provided byswitching power supply controller 1200. The operation of the SEPICcircuit will not be described here since it is well known to thoseskilled in the art. However, with regard to the switching signals to thegates of the transistors, it will be recalled that in a first phase FET3.3 conducts and in a second phase FET 3.3 is turned off and FET 3.4conducts. The timing and duration of the control signals to the gates ofthe transistors is determined by the signals from switching power supplycontroller 1200. Here again, as in the above-described buck and boostcircuits, the order of and duration of the gate control signals iscontrolled by switching power supply controller 1200 to provide thedesired output voltage V_(out) at a target constant value oralternatively at a constant current. The operation of circuit 1301.3 is,as with the other circuits which are controlled by switching powersupply controller 1200, is determined by a system configuration which isdescribed elsewhere herein. The configuration is programmed at theoutset of the operation of the power supply circuits connected toswitching power supply controller 1200. As described in more detailbelow, the operation of the circuits can be changed dynamically byswitching power supply controller 1200 as a function of the feedbackfrom the power supply circuit being controlled, the application ofexternal power, and among other things the voltage of batteries used inconnection with the circuit.

[0498] Switching power supply controller 1200 may also support otherpower supply configurations such as the half-bridge which is illustratedin FIG. 25 and FIG. 44. As explained more fully below, regulationcontrol module (REG) 1204 includes transfer functions and is programmedto provide the appropriate signals for controlling power suppliesconnected to the system. In one embodiment, DPC 1201 and NFET drivermodule 1202 are utilized to generate the control signals which areprovided to the gates of the power supplies connected to the system.

[0499] In switching power supply controller 1200 (FIG. 12), because thesampling function performed by SHM 1207 and the driving functions aremerely controlled by analog to digital converters in the case ofsampling functions, and digital logic in the case of the drivefunctions, it's a software task, or one method of implementation is tosimply apply the correct transfer function and sequence of control inorder to change topology. In this way, with the same internalstructures, drivers for the external FETs, sample and holds andmultiplexers, analog to digital converters for reading the inputvoltage, a variety of control loops supporting a variety of differentexternal topologies can be implemented without change in the external orinternal structure of the chip except with regard to the software thatruns within it.

[0500] We've demonstrated above three different topologies that are verydifferent, but it should be seen from this that actually any number ofdifferent topologies could be implemented so long as their transferfunctions are known and the circuit itself has been informed of theexternal topology and the interconnect of the external components.

Section 1.3.2 Buck, Boost, Sepic, Sync, Half-Bridge, Multi-Phase etc.from a Single Controller Structure

[0501] Referring to FIG. 12, it can be seen that in this implementation,there is a single regulation control module (REG) 1204 which controls avariety of outputs. By providing programmable information to thesoftware data set for each instance of the regulation softwareassociated with each output, different topologies (i.e., buck, boost)can be achieved on different outputs simultaneously. For example, oneset of outputs might be described to the regulation hardware block asbeing connected in the configuration of a buck converter. An adjacentset of outputs could be defined to the regulation hardware block as aboost converter or a half bridge, a sepic, or other topology. Regulationcontrol module (REG) 1204 then can dynamically by processing first onefeedback and then the next, switch between different topologies alloperating on different pads from the point of view of the externalsystem all operating simultaneously, but due to the sample nature of thedata and the digital nature of the pulse width modulation control, infact, a single regulation engine is processing each topology andfeedback strategy in time one after the other to maintain regulation onall pads simultaneously.

Section 1.3.3 on the Fly Topology Reconfiguration

[0502] In one implementation of the present invention, dynamicreconfiguration of a controlled power-supply is provided. In one mode,the controlled power supply may operate as a buck supply, in anothermode as a battery charger and in another a battery boost circuit.Referring to FIG. 46, an embodiment is illustrated in which the topologyof circuit 1300.2 can be changed by appropriate application of controlsignals to the gates of the transistors. For example, assume that noexternal power is being supplied and that Batt. Ø is at 3.1 volts.Further assume that circuit 1300.2 is running as a boost converter offof Batt. Ø and providing 3.5 volts to Supply A, which is driving Load Ithrough Supply 1. In this example, we further assume that Batt. Ø whenfully charged has an output of 4.2 volts. If external power (indicatedin the figure by Ext Pwr) is applied, of for example 12 volts, this isdetected by switching power supply controller 1200. Upon detecting thatexternal power is present, switching power supply controller 1200provides drive control signals to the gates of transistors QT_(Ø) andQB_(Ø) to operate circuit 1300.2 as a buck power supply, allowingcurrent to flow from the external power and be regulated through circuit1300.2 and then delivered to Batt. Ø at the correct current and voltageto affect charging of Batt. Ø. If Batt. Ø becomes fully charged, thenthe circuit 1300.2 could be switched off, or maintained in a tricklecharge mode to maintain the charge on Batt. Ø. The external power alsosupplies power to circuit 1301.2, which for illustration purposes, issupplying Load I at 3.3 volts via the bus called Supply A. In anothermode, assume that the external power is removed and that Batt. Ø iseither fully charged to 4.2 volts or charged to a voltage sufficientlyhigh to drive circuit 1301.2 directly from Batt. Ø. Switching powersupply controller 1200 detects that the external power has been removedby observing the drop in voltage of Supply A. Under these conditions,switching power supply controller 1200 will turn transistor QT_(Ø) oncontinuously and transistor QB_(Ø) will not be provided with gate drivesignals. Switching power supply controller 1200 operates in this modebecause it detects that Batt. Ø is providing an output voltage of 4.2volts or a lower voltage which is sufficient to supply voltage tocircuit 1301.2 in excess of the 3.5 volts which it needs to maintainregulation output to Load I at 3.3 volts. This state is maintained asthe battery is discharged through transistor QT_(Ø), through Supply Ainto circuit 1301.2. When switching power supply controller 1200 detectsthat Supply A has declined to 3.5 volts, which would represent a dutycycle of about 95% for circuit 1301.2, at this point it's clear thatwithout additional voltage at Supply A, it would not be possible tomaintain load regulation for V_(o) being provided by circuit 1301.2.Accordingly, switching power supply controller 1200 transitions circuit1300.2 to a third state, that is the state where the battery is lessthan 3.5 volts and switching power supply controller 1200 begins tooperate circuit 1300.2 as a boost converter, whose source is Batt. Ø andswitching power supply controller 1200 regulates boost operation toregulate Supply A at 3.5 volts. Switching power supply controller 1200can now maintain Supply A at 3.5 volts meeting the minimum requirementsof circuit 1301.2 until the battery is discharged or until externalpower is again available. This allows the system to provide outputvoltages which may be higher or lower than the input battery voltage andallows switching power supply controller 1200 to utilize circuit 1300.2in one of three modes: (i) as a buck converter to charge the battery;(ii) as a switch to supply battery voltage directly to Supply A throughQT_(Ø); or (iii) as a synchronous boost converter to allow operation ofcircuit 1301.2 to provide output voltages above the voltage availablefrom the Batt. Ø. The hardware for implementing the foregoing is shownin FIG. 12, and comprises central processing module (SYS) 1205,regulation control module (REG) 1204, sample and hold module SHM 1207,the output of which feeds analog to digital converter 1206. Also, NFETdrivers module 1202 are utilized to drive the gates of the transistors.

Section 1.3.4 Programmable Topology on a Multi-Output Controller

[0503] In order to provide support for different topologies in prior artsolutions, the same internal structures would actually have to changetheir sense of feedback, the way the pulse width modulation signal wasfed to the external FETs would have to be reversed, dead timesreinterpreted to mean something different that does not overlap, etc.The foregoing discussion on supporting multiple topologies from the samestructure indicates that if the fundamental elements were digital, thatis, the feedback information monitored from the outside were convertedto a digital signal and the control of the pulse width modulator outputswere also done digitally, that all of this could be accomplished insoftware; that is, the single structure could support multipletopologies. In order to make that a practical production product, it isnecessary for such a switching power supply to know at the instant ofactivation what sort of a supply it is supposed to be. This can-beaccomplished in a variety of ways. In one implementation, this could beaccomplished with external mode control pins, which could be soldered inone state or the other. A disadvantage to that strategy is that itwouldn't be possible to change the topology dynamically, which may bedesirable. For example, the circuit of FIG. 45 could be a batterycharger circuit, which is a buck topology for the purposes of chargingthe batteries which would be connected to V_(o), but later, underdifferent circumstances, when external power is no longer available andthe batteries are the source of power, that same external connectioncould actually represent a boost topology, where the input and outputvoltage samples are reversed in their significance and the duty cycle isreversed in its significance and new regulation is applied. Moreparticularly, circuit 1.3.1 would be converted to a boost circuit inwhich the battery connected to V_(o) becomes the V_(in) and the V_(in)would become V_(o). In this scenario, the direction of the currentindicated in FIG. 45 would, of course, be reversed. So it's desirable tobe able to change the topology on the fly and this can be accomplishedby providing mode control bits within the switching power supply itselfthat could be stored, for example, in a non-volatile memory 1216 (FIG.12), or could be changed under program control, for example, to go fromthe battery charging operating to boost operation.

Section 1.4 Discussion of Coulombmetric Measurement in a Switching PowerSupply Section 1.4.1 Cycle-by-Cycle Energy Extrapolation fromcurrent/Voltage Pulse Data

[0504] The current invention offers a significant improvement in asystem designer's ability to accurately measure, control, and predictthe energy available to the system from it's rechargeable battery orbatteries. Importantly, this is accomplished without additionalcomponents beyond those already provided for the buck/boost regulationsystem described. Many of the component parasitic values, described inconjunction with the regulation algorithms, are also reused. Finally,the current invention is more energy efficient and enables much-improvedaccuracy in determining the remaining battery energy at any givenmoment, which system designers may translate into longer battery life,smaller batteries, lower weight, smaller form factor, lower cost, or acombination of these.

[0505] The prior art does not provide a satisfactory method ofaccurately measuring the remaining energy capacity of a battery. Forexample, cellular phones typically rely upon measured voltage toindicate state of charge. However, if a low battery is recharged, evenfor a brief period of time, it will falsely indicate a full charge whenremoved from the charger. Since this is simply a measure of surfacecharge, not energy available, the user will experience the equivalent ofshort battery lifetime, perhaps even believing the battery is worn outand needs replacement.

[0506] Using coulombmetrics, one measures the actual energy delivered toand taken from a battery. Energy available can be influenced by suchfactors as the number of past charge/discharge cycles, cell temperature,charge/discharge rates and such. Fortunately, these factors do not haveto be precisely known if one knows how much net energy has been put intothe battery. The approach is to determine how much energy is put intothe battery, hence available for delivery, then measure said deliveryaccurately and alert the system monitor when certain conditions arereached. This is important for personal digital assistants (“PDAs”),notebook computers, and other devices which hold certain information involatile memory devices but can move the data to a nonvolatile media ifthe unreliability or failure of the volatile memory device is imminent.

[0507] For example, PDAs which utilize the WIN CE operating system(“OS”) must faithfully save the context of all open files and certainsystem variables before a complete shutdown with attendant loss ofvolatile memory. In fact, failure to save this data before loss ofadequate power may corrupt the OS, such that the product is renderedirrecoverably nonfunctional. For this reason, such products are notdesigned solely with user-removable batteries but rather with at leastone non-removable battery for memory keep-alive. The system designcannot just recognize when the energy is depleted, but must anticipatedepletion far enough ahead of time to allow adequate energy to save offthe critical data to a nonvolatile media.

[0508] Since determining battery energy from voltage alone is veryinaccurate, designers must allow a large margin. This causes the user toexperience a short battery life, since it is when the product ceasesoperation, not when the battery is actually depleted, that the userperceives the battery to be exhausted.

[0509] Another, better approach of the prior art is to use a measuringdevice associated with the battery. In notebook computers this device isoften inside the battery case itself. In PDAs it is an additional,costly device, external to the battery. As with the current invention,these schemes measure the power delivered to and removed from thebattery, as well as measure battery temperature to calculate the energyavailable. However both approaches suffer from a serious shortcoming:the sensing resistor needed to create a voltage drop sufficient tomeasure during low current draw (say, 2 millamperes in standbyoperation) must be relatively large, which then causes it to consume asignificant amount of power during high current operation.

[0510] A unique technique utilized in the present invention is toinstead accurately measure the power delivered from and provided to thepower supply/regulation system. An important aspect of the presentinvention is to indirectly measure current draw during low poweroperation without using a sense resistor. This resistor, which is neededfor regulation, may then be a low value such that there is little lossduring high power operation.

[0511] Referring to FIG. 46, one topology is illustrated showing asingle, multipurpose stage 1300.2 which can be used as battery chargerstage, and a single output stage 1301.2. In this configuration, assumeno power is externally supplied. The voltage of battery Batt. Ø mayrange from 4.2 to 2.7 volts. If, for example, the target value for V₀ is3.3 volts and we connect the Supply A rail directly to a 2.7 voltbattery, a buck converter will not work. In the present invention, whenthe battery voltage is 4.2 volts, we turn on FET QT_(Ø) and leave it oncontinuously, which supplies 4.2 volts to Supply A. Stage 1301.2 thenoperates as a buck converter. When the voltage of the battery approachesthe required output voltage V₀ of the buck converter, we begin operatingstage 1300.2 as a boost converter. More specifically we turn ontransistor QB_(Ø), causing inductor LØ to charge, then dischargeinductor LØ into capacitor C_(E) via transistor QT_(Ø) with transistorQB_(Ø) turned off. This allows operation all the way down to a batteryvoltage of 2.7 volts while maintaining a regulated 3.3 volts at V₀. Thetypical battery voltages will depend upon the technology of the batteryselected for the system.

[0512] There are two distinct techniques employed by the invention tomeasure power removed from the battery. One is appropriate for very lowcurrent drain conditions. During low current discharge and when circuit1300.2 is operated as a buck circuit, the time between gate pulses totransistor QT_(Ø) is typically very long. This is typical ofapplications in low power, wherein power is only needed due to leakageand supervisory circuits; usually a few milliamps or less. Referring toFIG. 46B, the higher current method is used when the inductor L3 isdriven during some portion of each cycle time. Note that continuous anddiscontinuous modes (defined elsewhere) utilize the same methodology.All of these techniques have the benefit of utilizing only thecomponents already employed for accomplishing regulation.

[0513] First let's examine the measurement of the power taken from thebattery during low current operation. One can monitor the powerdelivered by the battery Batt. Ø by measuring the voltage drop acrosssense resistor RØ. As discussed earlier, however, this would have thesame problem as the prior art, namely the necessity of a largeresistance to enable an adequate voltage drop for analog-to-digitalconversion (ADC), which would then cause a significant power loss duringhigh current operation. The present invention avoids this issue entirelyby instead monitoring the voltage across the Supply A capacitor C_(E).Since switching power supply controller 1200, FIG. 25) has an accuratetime base from the crystal oscillator, the power may be preciselydetermined by the formula I=C(dV/dt), where C is the value of capacitorC_(E). The change in Supply A voltage (measured by analog to digitalconverter 1206 shown in FIG. 12 relative to ground) is determined bymeasuring and recording the voltage at precisely known time intervals,which are under program control. The advantages of this method arenumerous, for example: (i) the value of resistor RØ, may be kept verysmall; (ii) all of the power removed from the battery is measured; and(iii) no additional components are needed. By measuring ΔV over arelatively long time period one eliminates noise or transient factorsfrom introducing errors. Although in FIG. 46 only two stages are shown,switching power supply controller 1200 may be controlling a plurality ofcircuits which are powered by Batt. Ø. It will be understood that thismethod of measurement is only appropriate when all power outputs beingdriven by Batt. Ø are in low current mode. If one output were in ahigh-current mode and others in low power (e.g., sleep) mode, theoutputs in low power mode would simply be ignored, a very small errorcompared with the energy utilized by the high power stage or stages.

[0514] In the above technique, the charge removed from the capacitor ismeasured over time. As described elsewhere, the system is informed aboutthe characteristics of the external components connected to it. Thesystem uses these values of the external components and utilizes them inthe coulombmetric calculation. This is important because since the exactcapacity of the battery is unknown, we measure how much goes in, wemeasure how much goes out, then correct for temperature and otherfactors which affect battery capacity.

[0515] Battery capacity varies from unit to unit, so there is no way toknow the capacity in one cycle. Products that utilize coulombmetrics aretypically inaccurate until they go through a charge/discharge cycle. Inthe method of the present invention, in low current mode, we measurevery, very low current without any efficiency loss which is suffered inthe prior art by having to use large values of resistance for the senseresistor. We also avoid the use of a very high resolution A to Dconverter because we are resolving time in our implementation. Time isthe factor where we have the most precision of all. The value ofresistors R1 and RØ depend upon the supply design, not the coulombmetricneeds. They would typically be in the range of 20 to 100 milliohms.

[0516] In accordance with the present invention for coulombmetricmeasurement in conditions of high and medium power delivery, a measureis made of the power delivered to the load. This will be equal to thepower removed from the battery, scaled by efficiency. This technique isalso useful for measuring the energy put into the battery duringcharging; the same technique is used, the battery simply being the load.The advantage is that what is measured is the net energy delivered tothe battery by the external supply, allowing the designer to ignorepower delivered during that time to the other loads. Thus the estimateof total power available from the battery remains one of keeping arunning total of net energy stored in the battery, consideringtemperature and other factors previously discussed.

[0517] Consider now the high current usage case. Current must bemeasured on a cycle by cycle basis. This is because power is deliveredto the load in some portion of every 2 μsec cycle, with the duty cyclebeing continuously recalculated and set to hold the voltage V₀ withinthe desired controlled interval. Referring again to FIG. 46, onesolution would be to measure the total current delivered by the batteryBatt. Ø by measuring the voltage across resistor RØ. However, to sampleout transients and noise would require frequent sampling throughout eachcycle, especially in systems with multiple outputs active. This wouldcreate a computing burden that would be equal to that of regulationitself. Instead, according to one technique of the present invention, adetermination is made of the power removed from the battery for eachcycle, using only one summing the power over many cycles.

[0518] A simplified implementation is described below using FIG. 46B inthe explanation. This scenario has a baseline current of 2 amps with aripple current of 200 milliamps, as depicted in FIG. 46A. That is, thetotal current swings from 1.9 to 2.1 amps. The technique of theinvention is to sample the current at its peak, which is known to occurjust before FET1 switches off and FET2 switches on. This is done bysampling the voltage across the output stage via sense lines S3 and S4using sense resistor R3. Although sense resistor R3 has a low value (asdiscussed in the low current mode description), current I is now highenough to cause an adequate voltage drop for A to D conversion.

[0519] The on time is known, the off time is known, therefore dt isknown for this stage. We know the output voltage (V_(o)) which ismeasured using sense line S4 and the input voltage (V_(in)=SupplyA),thus we know the voltage across the inductor L3 (V_(in)−V_(out)) and weknow the characteristics of inductor L3. This tells us how much energyis being delivered to the load on a 2 microsecond basis. Typically, thesystem reports coulombmetric information out ten times per second, avery fast update rate for coulombmetrics. By keeping a running total ofpower delivered to the load and knowing the efficiency and othercharacteristics of the battery, we have a very precise measure of thepower available from the battery at any moment. So for high currentscases, coulombmetric measurements are available from the method that weuse to perform regulation. No additional circuitry is required, only acalculations. In the prior art, one of the major jobs is to filter outnoise. The system of the present invention synchronously samples withthe noise source so there is no noise to filter since it is not seen atsampling time.

[0520] In the continuous mode, which is illustrated in FIG. 46D,(T_(Drive)+T_(Sync))=T_(Total)=2 μSec. As used herein, the phrase“continuous mode” means that current is flowing through the inductor forthe entire switching cycle. In a discontinuous mode, which isillustrated in FIG. 46C, the relationship is:(T_(Drive)+T_(Sync))<T_(Total).

[0521] Referring to FIG. 46D, an example is illustrated of the current Ithrough inductor L3 as a function of time over a 2 microsecond period,illustrative of continuous mode. In this example, a peak current of 200milliamps, indicated by I_(Pk), is achieved in one microsecond. Duringthe second microsecond of the period the current declines to zero.During the first half of the period, FET1 is conducting and FET2 isnon-conducting. During the second half of this period the conductionreverses. In this example, in the second half of this period the currentthrough inductor L3 has declined to zero, but has not reversed, as isthe case in some instances described herein. The period during whichFET1 is conducting is indicated in FIG. 46D as T_(Drive) and the periodduring which FET2 is conducting as indicated by T_(Sync). The total timefor the measurement period is indicated by T_(Total).

[0522] Now assume the system to be operating in the discontinuous modeas illustrated in FIG. 46C. The load requires an intermediate current,for example 25 ma. The time that it takes for capacitor C3 to decay isimmaterial because a pulse is being supplied in every cycle. We want apeak current of 100 ma and an average current during the first phase,from time 0 to 1 μsecond, of 50 ma and a total output current of 25 mafor the 2 usec period. Calculating 100 ma using R3 is difficult becausethe value of R3 is low, typically 0.05 ohms, and accordingly we havevery little resolution. However, in the circuit, we know that the valueof inductor L3 is 20 μh in this example. We know precisely what theinput voltage is (V_(in)=8V), what the output voltage is (V_(out)=4V),the time it was on (1 μsec) and that gives us the current that went intoinductor L3, the time that it was discharged and this gives us thecurrent that was flowing out of inductor L3 and we know the time it wasoff. Again, we can precisely calculate the load on a cycle by cyclebasis.

[0523] If the output voltage V_(out) were lower, it would take much lesstime to charge inductor L3 than to discharge it. If (V_(out)) were, forexample, 2 volts, we would have 6 volts across inductor L3 and thecurrent would ramp up more rapidly than down. From the foregoing, itwill be appreciated that all the numbers required to calculate thecurrent are available without actually directly measuring it. We providebelow a general equation for calculating the current going into theload. Instead of measuring current as is done in the prior art, onlytime and voltage measurements are required. The system takes thesemeasurements at a rate of 500,000 times per second, however,coulombmetric data is only updated 10 times per second by taking thesenumbers continually and averaging them.

[0524]FIG. 46E illustrates an example in which the coil current ofinductor L3 is 100 milliamps at the beginning of the drive period and atthe end of the drive period with the current flow in the direction of L3to R3. During time T_(Drive), FET1 is conducting and FET2 isnon-conducting and during the T_(Sync) period the conduction of the FETsis reversed. The total time period is indicated by T_(TOTAL). In thisexample, peak current I_(Pk) is greater than ripple current I_(Ripple).As will be appreciated, I_(Ripple) is equal to 200 milliamps and I_(Pk)is 300 milliamps. This, of course, results in (I_(Pk)−I_(Ripple))=100milliamps.

[0525] The average current per second flowing during the time periodsillustrated in the above examples may be determined by the formula:$\begin{matrix}{I_{{Avg}/\sec} = {{\frac{V_{in} - V_{out}}{L} \cdot \frac{1}{2} \cdot \frac{T_{DRIVE}}{T_{TOTAL}}} +}} \\{{{\frac{\varnothing - V_{out}}{L} \cdot \frac{1}{2} \cdot \frac{T_{SYNC}}{T_{TOTAL}}} +}} \\{{I_{Pk} - I_{Ripple}}}\end{matrix}$

[0526] where T_(SYNC) is the time required for the inductor current toreach zero in the discontinuous mode or (T_(Total)−T_(Drive)) incontinuous mode. Also, for the calculation above, it is assumed that thecurrent through inductor L3 is not allowed to go negative (i.e., flowfrom V_(out) toward terminal S); and that the peak current, I_(Pk),through inductor L3 is less than its saturation current.

[0527] The first term in the above equation represents the A portion ofthe current contribution indicated on the figures, the second term ofthe equation represents the B portion of the current indicated in thefigures and the final term is indicated by C which is the continuingcurrent that flows in inductor L3. It will be appreciated from the abovethat the current being delivered can be calculated using informationavailable in the system rather than being measured as is the case in theprior art. This greatly simplifies the task, as well as reducing thecircuitry required.

[0528] Note now an optional variant of discontinuous mode. As powerdemand from a stage is reduced, the duty cycle, hence T_(DRIVE) time, isreduced. When this time becomes small the switching losses of the FETscan become a significant loss of energy in the system. The same dutycycle may be achieved with less loss, hence better efficiency, by notturning on FET1 for one or more cycle times, thus averaging T_(DRIVE)and T_(SYNC) over this time which is now longer than (but a multiple of)2 μsec. This mode is called “the cycle skipping mode.” Note, then, thatthe above formula still applies, with T_(TOTAL) equal to the timeinterval between T_(DRIVE) pulses. It will be recognized, then, thatcontinuous and discontinuous modes are simply a special case whereinT_(TOTAL)=2 μsec.

Section 1.4.2 Total Energy Calculation from Multiple Channel Data

[0529] Consider an array of switching power converters as shown in FIG.47. This is an exemplary arrangement; there could be many otherarchitectures. As stated earlier, any output stage may be freelyconfigured as a buck converter (for example, stages SP1, SP2, SP3, SP4),or as a boost converter (for example, stages SP5, SP6). Stages SP5 orSP6, then, when connected to a battery, may simply connect the batteryto a supply bus SB #1 if the battery voltage is above what is needed forthe buck converters SP1-SP4. Alternately, switching power supplycontroller 1200 can configure converters SP5 and SP6 as boost converterswhen the voltage of the batteries are below what is required to meet theneeds of the buck converters, but above the minimum useable energy ofthe battery. Additionally, switching power supply controller 1200controls the charging of the batteries if charging is needed and anexternal supply is connected to bus SB1. Switching power supplycontroller 1200 selects between BAT5 and BAT6, depending upon the needsof the system and the energy available in each battery. For ease ofillustration, less than all of the control connections between switchingpower supply controller 1200 and converters SP1-SP6 are illustrated. Afull set of connections between switching power supply controller 1200and controlled converters are illustrated in other portions of thisspecification.

[0530] In this multiple-output system the energy state of BAT5 and BAT6(and of the two collectively) is determined by employing thecoulombmetric measurement techniques discussed herein, that is,determining the energy delivered by each of the converters SP1, SP2,SP3, and SP4, factoring in the efficiency of the system, as well ascertain battery parameters as detailed elsewhere. Then the power profileof the whole system is the sum of these elements. This information isreported to switching power supply controller 1200 for purposes of loadbalancing, load shedding, tuning an individual channel or system foroptimal efficiency, or identification of a problem or even failure.

[0531] Once this is understood, it will be appreciated that an array ofsystems such as that in FIG. 47 may be utilized and theinformation/control managed by a higher level control system. Oneexample is a telephone central office, where the system can detect aproblem in an area (e.g., cooling suddenly blocked to a specific area)or an individual card or supply channel (e.g., a short or open in one ofit's loads). As before, no additional hardware is needed, simply reuseof known data for another purpose.

Section 1.4.3 Battery Life-Time Estimate in an SPS

[0532] The above details the invention's determination of energy removedfrom a battery. To complete the system description, refer to FIG. 48.The system includes a battery source indicated as Batt. 1.4.3; a chargerboost circuit CB1, which can function as a charger when external voltageis provided, that is the battery can be a load to the CB1 supply and theenergy provided to battery 1.4.3 measured per the above descriptions;and a buck converter CB2. As explained more fully elsewhere in thespecification, circuit CB1 can operate as a switch when the batteryvoltage is above the voltage required by the buck converter CB2, or as aboost supply when the battery voltage is below the voltage required forthe buck supply CB2. Both of these power supplies are monitoring theenergy that is flowing through them and provide that information to theprocessing element 1.5 which can be part of switching power supplycontroller 1200. Processing element 1.5 also receives temperature datafrom temperature sensor element T.

[0533] Temperature sensor T may be a thermocouple, a thermal variableresistor, or it could be a Kelvin temperature sensor. In oneimplementation of the invention, a Kelvin temperature sensor is used.The integrated circuit also has pins to support an external Kelvintemperature sensor, depending upon the proximity of the integratedcircuit to the battery. Data from one or the other of the sensors, orboth, can be used. During charge cycles, the total amount of energy thatis provided to the battery is monitored, scaled with the batterytemperature using data provided by the battery manufacturer, and thetotal charge that the battery absorbs is computed. Batteries absorb morecharge when they are hot than they do when they are cold. Also, theyhave more energy available when they are discharged hot than when theyare cold. The worst possible combination is to charge it cold and use itcold. By using capacity degrade data to first compute how much energy isactually delivered to the battery, then monitoring the temperature andthe rate at which the charge is being removed from the battery by thebuck converter CB2, which reports its power information to processingelement 1.5, the time remaining until battery exhaustion is calculated.

[0534]FIG. 48A illustrates a typical battery degrade curve which plotscapacity (C) versus temperature (T). This information is published bybattery manufacturers. The battery degrade curve information may beprogrammed into processor 1.5.

[0535] In these applications the battery is known to the system. It iseither part of the system, or the power supply system is built into thebattery module. The battery degrade information about the batterycapacity can be stored in nonvolatile memory indicated by NVM1 in thefigure. It's also true that for families of battery chemistries thereare similar characteristics. So although the given capacity for somemanufacturers are better or worse, the decay rates, for example fornickel metal hydride batteries, are similar even if one does not knowthe data for that specific brand of battery. Clearly, the more stablethe temperature is, the less important the degradation data is.

Section 1.4.4 SPS Current·Voltage (Power) Regulation Based onCoulombmetric Data

[0536] In the previously described embodiment the coulombmetricmethodology may be used to accumulate and report energy consumption orinput.

[0537] An alternative implementation is for the coulombmetric data to beused as an input for regulation. With cycle by cycle energy as theregulated parameter in a control loop constant energy could be deliveredto a load or consumed from a source. This regulation could beaccomplished by adjustment on a cycle by cycle basis of the duty cycleof the FETs based on maintaining a constant coulombmetric (energy)value. One application of this technique would be to regulate the inputenergy to a radio frequency power amplifier for the purpose of powerlevel control. Another would be to regulate the power delivered by aphotovoltaic cell.

[0538] In the previously described embodiment the coulombmetricmethodology made use of certain voltage measurement obtained for use bythe regulation control program. That is, the coulombmetric algorithmprogram reuses voltage measurements (for example, the voltage acrosssense resistor R1 in FIG. 46) taken by the voltage regulation programand stored into a predetermined memory location.

[0539] An alternative implementation is for the coulombmetric programloop to take this data instead, and the regulation algorithm program canthen make use of the stored data. An advantage of the current inventionis the ability to take data only once, then make the data available forother purposes. By using the program control, the data of interest istaken during each cycle frame, and that the data is saved for reuse byother program(s).

[0540] The voltage control program (if that is the preferred method ofcontrol for a given output channel), then, would make use of said datameasured within the coulombmetric loop to control voltage as previouslydescribed. That is, adjustment on a cycle by cycle basis of the dutycycle of the FETs.

Section 1.4.5 SPS Constant Energy Output Regulation Mode

[0541] Previous descriptions of the application of the invention havefocused on voltage, controlled to remain within a certain target range.Having the capability to collect and utilize coulombmetric data permitsits use to instead control power directly. That is, the combination ofvoltage and current, not simply one or the other. This is beneficial forapplications where power must be kept within a target range, such as theRF output of a cell phone, or where control of the power level can leadto optimized efficiency, such as with a solar panel array. Recall thatthe invention develops this information with fine granularity andaccuracy on a cycle by cycle basis. This information may then be used tomanage the control loop.

[0542] A highly simplified example of a typical cell phone is shown inFIG. 49. The desire for best performance while keeping output below anagency-imposed maximum suggests the value of controlling to a specificpower level, say, 1 watt. Power supply 1.4A may be a buck or boosttopology, and typically the power amplifier 1.4 would have an efficiencyof 50%. The strategy then is to control the output of Supply 1.4A toprovide a constant 2 watts into power amplifier 1.4, compensating forchanges in voltage or current, depending upon temperature, and unit tounit variations. This is accomplished by using switching power supplycontroller 1200 to regulate power-supply 1.4A.

[0543] For another example, consider FIG. 49A. The system includes anarray of photovoltaic cells 1.4.3, which are essentially large silicondiodes. These diodes produce current at a voltage that is dependant upontemperature, influenced by approximately −2.1 mV per degree C. Therewould typically be one hundred such diodes in series, making the effectof temperature significant. The system may be arbitrarily operated atany of a range of voltage/current combinations, but only one combinationproduces the maximum power and that specific combination changes withtemperature. The maximum power is that combination that maximizes thearea under the V-I characteristic curve. Importantly, the need is tomatch the power delivered from the (solar array) source at theconditions that optimize the optional battery's charge acceptance rateand/or tuning for maximum power delivery to the grid.

[0544] One technique for determining the optimal set point is to makesmall changes in the output of buck converter 1.4.3.1 via switchingpower supply controller 1200, examining the resulting power usingcoulombmetric methods already discussed, then comparing the result tothe previous power level and selecting that which is highest. Theprocess is repeated, maintaining the array at its peak. As before, nonew hardware is required for this procedure.

Section 1.4.6 Charge Decay Time Energy Extrapolation

[0545] Referring to FIG. 41, regulation control module (REG) 1204includes a coulombmetric and temperature module 600.1. Becauseregulation control module (REG) 1204 receives voltage and currentfeedback information from the switching power converter, it can countthe number of coulombs of charge transferred from supply batteries tothe loads powered by the switching power converters. This provides amore accurate estimate of remaining battery life than by merely usingthe current battery voltage to estimate remaining battery life. Asdescribed further with respect to central processing module (SYS) 1205,the circuit parameters such as inductance values and capacitance valuesfor each of the switching power converters may be stored in memorywithin central processing module (SYS) 1205. By processing the feedbackinformation in light of these circuit parameters, coulombmetric andtemperature module 600.1 may determine the amount of coulombs suppliedby a battery. For example, if the feedback voltage from a switchingpower converter measures the voltage across a load capacitor, the amountof charge drawn through the capacitor is:

ΔQ=C * ΔV

[0546] Where C is the capacitance of the load capacitor, ΔV is thechange in voltage as determined from the voltage feedback samples, andΔQ is the amount of charge transferred to the load. It will beappreciated that the above example is illustrative only and thatcoulombmetric and temperature module 600.1 may determine the amount ofcharge transferred from a supply battery in other ways.

[0547] Coulombmetric and temperature module 600.1 may store theresulting charge measurements for central processing module (SYS) 1205to access through bus interface 525.1.

Section 1.5 Cyclic Switching Frequency Modulation

[0548] As described herein in section 1.1.4 and referring to FIG. 37 andFIG. 37B, a CAM 2486.4 illustrated may generate signals indicating pulserising and falling edges for a number of independent pulse channels asspecified by data from Regulation control module (REG). Each pulsechannel includes a number of pulses for controlling a correspondingexternal pulse-width-modulated (PWM) switching power converter. Duringstandard operation, CAM 2486.4 receives a read command in the form of acount from a counter, for example, a Grey counter 2484.4, that commandsCAM 2486.4 to check each possible data storage location to see ifregulation control module (REG) 1204 has written a data word in a givendata storage location matching the current count.

[0549] In one embodiment, CAM 2486.4 has storage for 64 data words.These 64 data words correspond to 8 pulse channels, wherein each pulsechannel defines 4 pulses. Seven of the pulse channels are used forexternal PWM-switching power conversion and the eighth pulse channel isused to generate auxiliary pulses For the seven pulse channels, 56 datawords need be specified. The remaining eight data words correspond tothe 4 auxiliary pulses edges of an auxiliary signal AUX 2446.4 used forexample to synchronize external circuitry.

[0550] As Grey counter 2484.4 counts through a complete cycle, it causesCAM 2486.4 to check its stored data words for any matches. Each cycle ofGrey counter 2484.4 defines a single DPC frame as shown in FIG. 37. Inturn, it can be seen that the clocking of Grey counter 2484.4 controlsthe minimum distance between possible pulse rising and falling edges.

[0551] For example, suppose Grey counter 2484.4 is a 10-bit counter andreceives a 268.4 KHz clock signal. If Grey counter 2484.4 is configuredto count at both the rising and falling edges of the clock signal, Greycounter 2484.4 will then count at a 536.9 MHz rate. The resulting DPCframe rate, which equals the count rate divided by the maximum count,will be 524.3 KHz (536.9 MHz/1024), wherein each DPC frame is dividedinto 1024 possible pulse rising and falling edge locations separated bya duration of approximately 2 nanoseconds. The division of each DPCframe into these possible rising and falling edge locations determinesthe minimum pulse-width-modulation (PWM) resolution for any PWMswitching power converter being controlled by a given pulse channel.Thus, the count rate for Grey counter 2484.4 determines the minimum PWMresolution as given by the inverse of the count rate.

[0552] As can be seen in FIG. 37B, the count rate for Grey counter2484.4 will ultimately depend on DPLL clock signal PLLCK 2460.4 fromDPLL 2480.4. Because DPLL clock signal PLLCK 2460.4 is used for multiplepurposes throughout switching power supply controller 1200, such as arelatively fast clock necessary for analog to digital converter 1206,PLLCK 2460.4 having a frequency of 536 MHz may be divided in spreaderdivider 2482.4 to clock Grey counter 2484.4 at a lower clock frequencyof, e.g., 268 MHz.

[0553] Regardless of the specific frequency Grey counter 2484.4 isclocked at, the count rate and the number of bits used in Grey counter2484.4 determines the DPC frame rate and the minimum PWM resolution. Therising and falling pulse edges for a plurality of external PWM-switchingpower converters are determined with respect to this minimum PWMresolution. The FET switches in each PWM-switching power converter willswitch on and off at the DPC frame rate. Accordingly, each PWM-switchingpower converter will produce RF noise at the DPC frame rate frequency.

[0554] To assist in the reduction of this RF switching noise, spreaderdivider 2482.4 includes a divider 200.1 and a spectral spreader 210.1 asshown in FIG. 50. Divider 200.1 receives DPLL clock signal PLLCK 2460.4from DPLL 2480.4 and provides a divided clock signal 215.1 to spectralspreader 210.1. Spectral spreader 210.1 dithers the frame rate so as tospread the RF switching noise in a spread spectrum fashion. By skippingor “swallowing” various clock cycles received from divider 200.1,spectral spreader 210.1 may achieve this dithering. In turn, spectralspreader 210.1 will skip clock cycles in divided clock signal 215.1 toproduce a desired amount of dithering to the DPC frame rate by providingan adjusted clock signal 220.1 to Grey counter 2484.4.

[0555] An exemplary embodiment for spectral spreader 210.1 is shown inFIG. 50A. A divider 300.1 and a counter 310.1 receive divided clocksignal 215.1. Divider 300.1 provides a secondary divided clock signal320.1 to an up/down counter 330.1, which in turn provides an up/downcount 335.1 to control a multiplexer 340.1. Multiplexer 340.1 selectsbits from a count 345.1 produced by counter 310.1 As controlled byup/down count 335.1, multiplexer 340.1 chooses either the mostsignificant bit or successively less significant bits from count 345.1to provide a selected bit 355.1 to the D input of a D-type flip-flop350.1 that is clocked by divided clock signal 215.1. A NAND gate 360.1receives both selected bit 355.1 and a Q output 365.1 of flip-flop350.1. Finally, an AND gate 370.1 receives an output 375.1 from NANDgate 360.1 and divided clock signal 215.1 and outputs adjusted clocksignal 220.1.

[0556] Accordingly, if NAND output 375.1 is true, the cycles of adjustedclock signal 220.1 will correspond to the cycles of divided clock signal215.1, that is, no skipping occurs. However, if NAND output is falseduring a given cycle in divided clock signal 215.1, this cycle will beskipped in divided clock signal 215.1. It will be appreciated that thenumber of skipped cycles, and hence the amount,of spectral spreadingdepends upon the sizes of counter 310.1 and up/down counter 330.1 andthe division provided by divider 300.1. For example, suppose dividedclock signal is 268 MHz, divider 300.1 divides by 1024, up/down counter330.1 is a 3-bit counter, and counter 310.1 is a 15 bit counter(corresponding to the 2 nanosecond PWM resolution discussed previously).Secondary divided clock signal 320.1 thus cycles according to the DPCframe rate. Initially, up/down count will be at zero such thatmultiplexer 340.1 selects the most significant bit in count 345.1. Whenup/down count 335.1 increments, multiplexer 340.1 will then select thenext-most significant bit and so on. It follows that the following pulseskipping schedule will be followed:

[0557] 1 pulse in 32 frames skipped (in a duration of 32 frames)

[0558] 1 pulse in 16 frames skipped (during the next 16 frames)

[0559] 1 pulse in 8 frames skipped (during the next 8 frames)

[0560] 1 pulse in 4 frames skipped (during the next 4 frames)

[0561] 1 pulse in 2 frames skipped (during the next 2 frames)

[0562] 2 pulses in 1 frame skipped (during the next frame)

[0563] 4 pulses in 1 frame skipped (during the next frame)

[0564] 2 pulses in 1 frame skipped (during the next frame)

[0565] 1 pulse in 2 frames skipped (during the next 2 frames)

[0566] 1 pulse in 4 frames skipped (during the next 4 frames)

[0567] 1 pulse in 8 frames skipped (during the next 8 frames)

[0568] 1 pulse in 16 frames skipped (during the next 16 frames)

[0569] 1 pulse in 32 frames skipped (in a duration of 32 frames)

[0570] whereupon the entire pulse-skipping schedule would be repeated.As a result, the DPC frame rate will vary in a nonlinear fashion. Itwill be appreciated that numerous other pulse skipping schedules couldbe implemented using alternative embodiments of spectral spreader 210.1.For example, the DPC frame rate could be varied in a linear fashion.

Section 1.6 PS/PM/Fault Management Integration—see Disclosure in DataSheet Section 1.6.1 Load Shedding in an SPS

[0571] Central processing module (SYS) 1205 may be initialized by a hostprocessor with the operating parameters and topology for a plurality ofswitching power converters under the control of switching power supplycontroller 1200. These operating parameters may include operatingthresholds such that central processing module (SYS) 1205 will cause theoperation of a given switching power converter to cease if thecorresponding thresholds are not satisfied. These operating thresholdsmay comprise a minimum supply voltage required for a given switchingpower converter or the minimum amount of charge remaining in a batteryor set of batteries used to power the switching power converter.

[0572] Microprocessor core 400.1 (FIG. 56) in central processing module(SYS) 1205 monitors these operating thresholds and responds accordingly.For example, microprocessor core 400.1 receives an interruptperiodically to update coulomb-metric measurements and batterytemperature readings with respect to the power supplies powering thevarious switching power converters under control of switching powersupply controller 1200. In conjunction with these coulomb-metricupdates, microprocessor core 400.1 may check that the amount of chargeremaining in the battery or set of batteries is sufficient to sustainthe respective supplies until the next checking interval. In conjunctionwith the coulomb-metric updates, microprocessor core 400.1 may alsocheck that the associated supply voltages satisfy the voltage minimumsfor the various switching power converters.

[0573] Should the amount of charge remaining/or the supply voltage notsatisfy the specified minimum for a given switching power converter,microprocessor core 400.1 uses a configured deterministic algorithm andcommands regulation control module (REG) 1204 to cease operation of theappropriate switching power converter. At the same time, microprocessorcore 400.1 notifies the host processor (not illustrated) that theparticular switching power converter is being brought down. In thisfashion, a “load shedding” is accomplished with respect to the loadspowered by the switching power converters being brought down. It will beappreciated that this manner of load shedding is efficient as comparedto a conventional method of using the host processor to monitor variousswitching power converters and directly commanding them to turn offshould an operating threshold be exceeded because a host processor willtypically demand far more power than microprocessor 400.1 would inresponding to interrupts to check the operating thresholds.

Section 1.6.2 Power Cycling in an SPS

[0574] Upon expiration of Host watchdog timer 1.1 shown in FIG. 53, areset signal/command is issued to a host microprocessor (notillustrated). However, in certain malfunctions such as latch-up, a hostmicroprocessor will not respond to a reset status notification orphysical reset signal assertion. Instead, a latched-up hostmicroprocessor will continue to draw current until its power source isexhausted or shut off. Assuming that its transistors have not beendamaged by the latch-up, the host microprocessor may then be reset.

[0575] Central processing module (SYS) 1205 has the ability to providean intelligent response to such malfunctions. Once a host watchdogexpires the host is notified by either a physical reset assertion or areset status notification (via an Interrupt and command response). TheCentral processing module then restarts the host watchdog and if thehost does not attempt to enable(kick) the watchdog within a configurablenumber of watchdog expirations the power supplies associated with thehost (configurable) is cycled off for a configurable time duration andrestarted. For example, a certain voltage level may be needed for thehost CPU's memory, another for its input/output circuitry, and otherlevels for the CPU itself, where each voltage level is provided by aswitching power converter under the control of switching power supplycontroller 1200. Stored in the Non Volatile Memory are the correct powersequencing for the host CPU's switching power converters for both apower up and a power down sequence. After power down has been completed,central processing module (SYS) 1205 may then power up the host CPU byappropriately sequencing the involved power converters.

[0576] Upon expiration of 8051 watchdog timer 5.1 shown in FIG. 53, areset may be issued to the internal microprocessor (not illustrated)causing a warm boot of the internal microprocessor. This reset may notcause the regulation of power to be interrupted rather it merelyrestarts the internal microprocessor. Additionally there may be a statusbit indicating a watchdog event occurred for the internal microprocessorto read upon rebooting to allow it to ascertain the reason for booting.

Section 1.6.3 Reset Conditioning in an SPS

[0577] As described with respect to watchdog controller 1213 of FIG. 53,switching power supply controller 1200 may reset a host CPU (notillustrated) by asserting a reset signal if Host watchdog timer 1.1expires. Because of the intelligent control provided by centralprocessing module (SYS) 1205, the reset may be asserted until certainconditions are satisfied. For example, regulation control module (REG)1204 may signal to central processing module (SYS) 1205 that certainswitching power converters are producing voltage levels outside of adesired operating range. For example, the output voltage of a switchingpower supply providing power to the memory of the host CPU may be out ofrange causing the host to not provide the appropriate resetcommand/signal. In such a case, central processing module (SYS) 1205could continue to assert the reset signal until all power suppliesaffecting operation of the host CPU are providing voltages withindesired operating ranges.

Section 1.6.4 and x.3, watch Dog Structure and Watch Dog Timer in an SPS

[0578] Because switching power supply controller 1200 may supply powerto a host CPU-containing device such as a personal digital assistant(PDA), watchdog controller block 1213 (FIG. 12) may provide a watchdogfeature for the host CPU. A common problem for operating systems runningon CPUs is a “lock-up” condition resulting from conflicting programcommands, invalid memory access requests, and related matters. Recoveryfrom such problems may take an extended, unknown amount of time or maynot occur. Accordingly, watchdog timers comprising a digital counterthat counts down to zero from a predetermined starting number are oftenimplemented in CPUs to avoid lock-ups. During normal operation, the CPUwill periodically command the watchdog timer to reset the counter toavoid the timer's expiration. However, in a lock-up, the CPU will notcommand the watchdog timer to reset the counter whereby the timerexpires. In response, a reset may then be initiated to remove thelock-up.

[0579] Because switching power supply controller 1200 includes centralprocessing module (SYS) 1205, the watchdog controller block 1213includes two types of watchdog timers as seen in FIG. 53: a hostwatchdog timer 1.1 for an external host CPU and a 8051 watchdog timer5.1 for the internal mocroprocessor.

[0580] If host watchdog timer 1.1 expires, watchdog controller 1213notifies central processing module (SYS) 1205 via an interrupt. Inresponse to this interrupt, central processing module (SYS) 1205 eitherasserts a reset signal to the host or asserts an interrupt line to thehost as is dictated by a configuration parameter.

[0581] If 8051 watchdog timer 1.1 expires, watchdog controller 1213 willassert the reset line central processing module (SYS) 1205. Thistriggers a warm boot of the internal microprocessor.

[0582] Watchdog controller 1213 may have two modes of operation: normalmode and power save mode. In the normal mode, both host watchdog 1.1timer and 8051 watchdog timer 5.1 are operative. In the power save mode,the host microprocessor is required to disable the host watchdog priorto issuing a power save command unless there is not a communicationslink between the host and the SPS upon which the Watchdog controller1213 will rely on a configuration parameter that specifies automatichost watchdog enabling/disabling upon application of or removal of powerassociated with the host.

[0583] Each watchdog timer 1.1 and 5.1 may associate with its ownservice register (not illustrated) used to reset the timers. To resetits particular watchdog, central processing module (SYS) 1205 writes apredetermined code word and the inverse of that code word to arespective service register. An errant write to a service register doesnot reset the associated watchdog timer and generates an interrupt tocentral processing module (SYS) 1205. In addition, the host watchdogtimer 1.1 may have its counter reset based upon a toggled binary signalreceived from the host microprocessor. This signal is processed bycentral processing module (SYS) 1205 which in turn resets the watchdog.However, resets using the kick watchdog command are more secure and lesssusceptible to runaway conditions in the host microprocessor.

[0584] To provide greater control flexibility to the host processor,Host watchdog timer 1.1 and 8051 watchdog timer 5.1 may be initializedaccording to data stored in associated configuration registers (notillustrated). By writing to these registers, the duration of theindividual watchdog counter timeout periods can be configured. Forexample, this configuration could be 15 bits for the host watchdog toaccommodate a range of 1 ms to ˜32 seconds while 6 bits could be usedfor the 8051 watchdog to provide a range of 100 ms to 3.2 seconds. If agiven watchdog timer is not enabled, the watchdog timer will not bestarted until its configuration register is re-initialized. To preventerrant access of the 8051 watchdog configuration register, thisregisters may be written to only once after a reset operation (until thesubsequent reset operation, whereupon the configuration register may bere-initialized). The host watchdog register may not have thisrestriction.

[0585] As discussed above, the host watchdog may issue an interrupt tocentral processing module (SYS) 1205 should host watchdog timer 1.1expire. A watchdog interrupt status register 15.1 may also store a bitto indicate that either watchdog's service register has been servicedwith an errant codeword, potentially signaling an invalid memory access.A watchdog interrupt mask register 15.1 (shown combined with thewatchdog interrupt status register in FIG. 53 for illustration clarity)may store bits indicating whether the host watchdog timer has beenmasked. In this fashion, central processing module (SYS) 1205 mayprevent watchdog controller 1213 from generating interrupts duringsystem critical periods. In addition, watchdog interrupt mask register15.1 may store a bit indicating whether interrupts resulting from anerrant codeword write to the service register for Host watchdog 1.1should be masked.

Section 1.6.5 Programmable Reset and Watchdog Functions

[0586] As described with respect to watchdog controller 1213 of FIG. 53switching power supply controller 1200 may reset a host microprocessor(not illustrated) if host watchdog timer 1.1 expires by asserting areset signal. Because of the intelligent control provided by centralprocessing module (SYS) 1205, the reset may be asserted until certainconditions are satisfied. For example, regulation control module (REG)1204 may signal to central processing module (SYS) 1205 that certainswitching power converters are producing voltage levels outside of adesired operating range. For example, the output voltage of a switchingpower supply providing power to the memory of the host microprocessormay be out of range. In such a case, central processing module (SYS)1205 could continue to assert the reset signal until all power suppliesaffecting operation of the host microprocessor are providing voltageswithin desired operating ranges.

[0587] Once all conditions have been satisfied, central processingmodule (SYS) 1205 allows the reset to be de-asserted. However, eventhough all power supplies are operating correctly, a host device maystill not have stabilized properly to justify release of the resetcommand. Accordingly, the duration of the reset command after allconditions have been satisfied may be programmable. The duration may bestored by central processing module (SYS) 1205 as programmed by a user.

Section 1.6.6 Resistive Digitizer in Combination with an SPS

[0588] Quad-Slope Analog to Digital Converter 1211 a in one embodimentof the present invention measures the point of contact between twosheets of resistive material. Touch screens suitable for implementingthe present invention are commercially available from manufacturers suchas 3M. FIG. 18B is a highly simplified illustration of a four-contacttouch-screen 18.8 having a first sheet 18.81 and a second sheet 18.82.These sheets are shown offset for ease of illustration, but are ofcourse aligned for normal use. Each sheet has a uniform sheet resistancesuch that the physical point of contact along the surface of each sheetmay be represented by the proportion of end to end resistance at thatpoint. Using sheet 18.82 and applying an electrical potential toterminals TOP 18.83 and BOT 18.84 permits, using the other sheet as acontact sheet, a determination of the point of contact in the Ydirection. Applying an electrical potential to terminals LFT 18.85 andRHT 18.86 using sheet 18.81 as a sensing sheet, permits, using sheet18.82 as a contact sheet, a determination of the point of contact in theX direction. Thus in each case a voltage is applied across one of thetwo sheets (e.g., 18.81 or 18.82, the “sensing sheet”) while it iselectrically isolated from QSADC 1211 a, and simultaneously an ADCconversion is made of the voltage present at the point of contact on theother sheet (i.e., 18.82 or 18.81, the “contact sheet”).

[0589] A voltage is applied to terminal LFT 18.85 and terminal RHT 18.86of the X coordinate sheet 18.81, then the proportion of the appliedvoltage can be read at either the TOP terminal 18.83 or BOT terminal18.84 of the Y coordinate sheet 18.82. The magnitude of the voltage readis representative of the physical horizontal position of the point ofcontact between the two sheets. Similarly, if a voltage is applied toterminal TOP 18.83 and BOT 18.84 of the Y coordinate sheet 18.82, thenthe proportion of the applied voltage read at either terminal LFT 18.85or terminal RHT 18.86 of the X coordinate sheet 18.81 is representativeof the physical vertical position of the point of contact between thetwo sheets.

[0590] In another embodiment, one resistive sheet is used for both X andY sensing while the other sheet is used to transfer the proportionalvoltage to the QSADC. A highly simplified illustration of a five-contacttouch screen 18.9 is shown in FIG. 18C. A highly simplified illustrationof a five-contact touch screen 18.9 is shown in FIG. 18C, and includessensing sheet 18.93 and contact sheet 18.92. Touching the front sheet18.92 causes 18.92 and 18.93 to contact each other. As in theillustration above, the sheets are shown off-set for ease ofillustration. In this embodiment where five connections are used, avoltage is imposed between the terminals LFT 18.94 and RHT 18.95 ofsheet 18.91, then the proportion of the voltage read at terminal 18.96of contact sheet 18.92 is proportional to the physical horizontalposition of the point of contact between the two sheets. Similarly, avoltage is imposed between the TOP terminal 18.97 and BOT terminal 18.98of sheet 18.93, then the proportion of the voltage read at terminal18.96 of contact sheet 18.92 indicates the physical vertical position ofthe point of contact between the two sheets.

[0591] Quad-Slope Analog to Digital Converter (QSADC) module 1211 a(FIG. 17) includes a custom low-power mixed-signal circuit that has bothanalog and digital input and output signals, including analog anddigital power and ground reference voltages. QSADC module 1211 ameasures and digitizes, to 8 bits of resolution, the voltages at twoseparate external ports relative to a voltage reference VREFH. In oneembodiment, a conversion rate for QSADC module 1211 a is approximately300 sps (samples per second).

[0592]FIG. 16 is a timing diagram illustrating the quad-slope (i.e.,dual conversion) analog to digital conversion (ADC) operations carriedout in the QSADC module 1211 a. Time intervals 1601 and 1602 (i.e.,“measurement periods” PMA and PMB) are equivalent fixed time durationscorresponding to 256 counts of a reference timer or counter. During timeperiods 1601 and 1602, the positive slopes of signal trace segments 1603and 1604 reach voltages V_(Y) and V_(X), plus the small initial voltage,which represent the integration of the signals being measured on thecontact sheets by the QSADC module 1211 a over time periods 1601 and1602.

[0593] During time intervals 1605 and 1606 (“conversion periods” PCA andPCB), signal trace segments 1607 and 1608 have identical negativeslopes, tracing the voltages as they decline from voltages V_(Y) andV_(X) to zero. During these conversion periods (PCA and PCB), thenumerical counts represent direct analog to digital conversions of themeasured voltages from contact sheets 18.82 and 18.81, respectively. Atthe completions of the conversion periods, end-of-conversion (EOC)pulses are generated (e.g., at times t₁ and t₂) to signal the end ofeach analog to digital conversion and to reset and zero the offsets ofthe analog circuitry in QSADC module 1211 a to prepare for subsequentconversions.

[0594]FIG. 17 is a block diagram showing the interface signals of QSADCmodule 1211 a in one implementation. As shown in FIG. 17, QSADC module1211 a includes: (a) Analog I/O interface (AIO) 1701, Digital Interface(DI) 1702, and the Power Supply Interface 1703. Analog I/O interface(AIO) comprises analog bi-directional measurement terminals 1701 a and1701 b (i.e., terminals TOP and BOT), analog bi-directional measurementterminals 1701 c and 1701 d (i.e., terminals RHT and LFT), analogreference capacitor ports 1704 a and 1704 b (PR1 and PR2, respectively),analog bi-directional measurement port 1701 f for the MID input, andReference Voltage signal 1701 e (i.e., reference voltage VREFH).

[0595] Analog I/O interface 1701 operates in two modes. In a first mode(“primary mode”) a port (e.g., Port X or Port Y) measures voltage by thetechnique described herein. Port X is comprised of switches A0, A1, A2and A3 (FIG. 18A). Port Y is comprised of B0, B1, B2 and B3 (FIG. 18A).In a second mode (“sleep mode”) ports X and Y are configured to detectelectrical continuity between them. A determination of continuitybetween Port X and Port Y indicates contact with the touch screen, whichthen causes the analog I/O interface 1701 to enter primary mode.

[0596] Digital interface 1702 comprises 8-bit output buses 1702 a(DOUTX[7:0]) and 1702 b (DOUTY[7:0]) for displaying digital results ofthe conversions at ports X and Y, respectively, completion or “DONE”signal 1702 c, Continuity Detection or “CONT” signal 1702 d, StartConversion or Reset “START/RSTN” signal 1702 e, 128 KHz 50% duty cyclereference clock signal (“CLK”) 1702 f, and Mode Select signal SEL 1702g. START/RSTN is the start control pin used to initiate the analog todigital conversion processes. When the START/RSTN pin goes HIGH theprocessing starts and subsequent conversions will not be initiated untilthe START/RSTN pin toggles LOW then HIGH again. When START/RSTN is heldLOW, all necessary circuits in the block are held in a low power resetstate. Signal SEL 1702 g is received from touch screen interface 1211,and is used to control the ADC conversion mode. When the SEL 1702 g portis LOW the MID port is not used for ADC measurements. That is, afour-terminal arrangement for measurement of X-Y position is employed,as shown in FIG. 18C. When the SEL 1702 g port is held HIGH the MID portis used for measuring the input voltage at the X and Y ports. That is, afive-terminal arrangement for measurement of the X-Y position isemployed, as shown in FIG. 18C.

[0597] The DONE signal at terminal 1702 c is asserted when the digitalconversions at both ports X and Y are completed, to signal that resultscan be read from output buses 1702 a and 1702 b (i.e., DOUTX and DOUTYbuses). The CONT signal indicates detection of continuity between portsX and Y.

[0598] Power supply interface 1703 comprises analog power and groundreference signals 1703 a and 1703 b (i.e., analog power and groundreference signals AVD and AVS, respectively), and digital power andground reference signals 1703 c and 1703 d (i.e., digital power andground reference signals VDD and VSS, respectively).

[0599]FIG. 18 and FIG. 18A show one implementation of QSADC module 1211a, in accordance with the present invention. FIG. 18 is a top-levelblock diagram of QSADC module 1211 a, including analog (ANLG) block1801, digital controller (CNTRL) block 1802, pre-settable up/downcounter block 1803, 8-input NAND gate 1806, and 8-bit Registers 1804 and1805 (i.e., registers REGX and REGY, respectively).

[0600] Table 2.6 provides a brief descriptive summary of the signalsshown in FIG. 18. TABLE 1.6.6a Destina- Port Name Type DescriptionSource tion TOP Analog Max Analog AIO Measurement Port BOT Analog MinAnalog AIO Measurement Port RHT Analog Max Analog AIO Measurement PortLFT Analog Min Analog AIO Measurement Port MID Analog Analog MeasurementAIO Port for the MID Input PR1 Analog External Reference AIO CapacitorFirst Port PR2 Analog External Reference AIO Capacitor Second PortSTART/RSTN Input Start Conversion TSI Port Active HIGH SEL Input ModeSelect TSI Conversation Port QSADC_CLK Input Clock CLKGEN DOUTX[7:0]Output Digitized Bus TSI For Measured Values A DOUTY[7:0] OutputDigitized Bus TSI For Measure Values B DONE Output Done Port TSI ActiveHIGH CONT Output Continuity Detection TSI Port Active HIGH VREFH InputHigh Analog IVS Voltage Reference VREFL Input Low Analog IVS VoltageReference AVD Power Analog Power IVS AVS Power Analog Ground IVS VDDPower Digital Power IVS VSS Power Digital Ground IVS

[0601]FIG. 18A shows one implementation of ANLG 1801 of FIG. 18, whichincludes operational amplifier 1851 and analog comparator 1852, inaddition to MOS transmission gates 1853 a to 1853 p, inverter 1854, ANDgate 1856, Digital Control block (DCNTL) 1855, and Level Shifter 1856 .The common mode ranges of the operational amplifier 1851 and analogcomparator 1852 are rail to rail (i.e., 0 to 3.3V).

[0602] DCNTL block 1855 generates the control signals necessary tocontrol the MOS transmission gates 1853 a to 1853 n. For convenience,the MOS transmission gates 1853 a to 1853 p are referred to as“switches” and each switch is designated by its control input signal(i.e., A0-A3, B0-B3, MEAS, SLP, EOC, SEL, CONV, and CONV2).

[0603] Initially, QSADC module 1211 a is in sleep mode, where electricalcontinuity is checked. A four-terminal arrangement is illustrated byFIG. 510. Switches 1853 b, 1853 c, 1853 h, 1853 i, 1853 n, 1853 l, and1853 f (i.e., signals A0, A2, B1, B2, MEAS and SLP) are closed, whileall other switches are open. When there is no electrical continuitybetween the two sheets, the output voltages of operational amplifier1851, analog comparator 1852, and the DOUT signal are all low. Afive-terminal implementation is illustrated in FIG. 51P. Switches 1853p, 1853 i, 1853 n, 1853 l and 1853 f (i.e., signals B1, B2, SEL, MEASand SLP) are closed while all others are open. When there is noelectrical continuity between the two sheets, the output voltages ofoperational amplifier 1851, analog comparator 1852, and the DOUT signalare all low.

[0604] When electrical continuity is established between ports Y and X,the output terminal of switch 1853 n (i.e., the non-inverting inputterminal of operational amplifier 1851) is pulled to a high voltage, sothat the output terminal of analog comparator 1852 is at a high voltage.The output terminal of analog comparator 1852 is the “DOUT” terminal ofanalog block 1801 (FIG. 18), which is connected to the “DIN” terminal ofdigital control block 1802. In response to the high voltage at theoutput terminal of analog block 1801, the CONT terminal (i.e., terminal1702 d at FIG. 17) is driven to a high voltage, resulting in QSADCmodule 1211 a exiting the sleep mode, and entering the primary mode.

[0605] In primary mode (entered when the CONT signal is at a highvoltage), when an active START/RSTN signal at terminal 1702 e isreceived from touch screen interface 1211, digital control block 1802begins a measurement cycle of the voltage at Port Y by presettingup/down counter 1803 to hexadecimal FF (i.e., FFh), thereby resettingthe CONT signal, and beginning the measurement and conversion process.Thereafter, each rising edge of the CLK signal at terminal 1702 fdecrements up/down counter 1803 until the count reaches zero (for atotal of 256 counts), which is decoded by NAND gate 1806 to activate theZERO signal received into digital control block 1802.

[0606] The operation of analog circuit 1801 is described below inconnection with FIG. 51F through FIG. 510. For convenience ofillustration, a dark line is shown on the figures to denote theconduction path of the transmission gates.

[0607] The measurement initial state is shown in FIG. 51F. In theinitial condition of the QSADC 1211 a prior to a measurement cycle,CNTRL circuit 1802 drives EOC HIGH and MEAS LOW, thus asserting CONVfrom inverter 1854. Switch 1853 e connects the non-inverting input toamplifier 1851 to VREFL. Amplifier 1851 is connected to thenon-inverting input of amplifier 1852, which has its non-inverting inputpermanently connected to VREFL. The output of amplifier 1852 isconnected to the inverting input of amplifier 1851, completing anegative feed back loop spanning both amplifiers. Amplifier 1851 bringsits inverting input to the same potential as VREFL (the current value ofits non-inverting input), plus any input offsets, by driving through thenon-inverting input of amplifier 1852. Amplifier 1852 brings itsnon-inverting input to the same potential as VREFL (the value of itsinverting input) plus any input offsets by driving through the invertinginput of amplifier 1851. The output of amplifier 1851 will be at VREFLminus the offset of amplifier 1852. The output of amplifier 1852 will beat VREFL minus the offset of amplifier 1851. Therefore capacitor 1860will have the difference of the offsets of the two amplifiers impressedacross it, effectively zeroing the offsets of the circuit. This is thecondition to which the circuit will return at the conclusion of eachconversion. Note that this configuration is the same for both a four andfive connection arrangement (i.e., FIG. 18A and FIG. 18B).

[0608] Referring to FIG. 51G, a conversion to read the position ofcontact with the Y coordinate sheet (18.82 in a four-contactimplementation) connects VREFH to TOP (18.83) of the Y coordinate sheetand VREFL to BOT (18.84) of the Y coordinate sheet. The SEL signal isLOW. At the point of contact with the X coordinate sheet a voltage isdeveloped which is proportional to the Y coordinate of the point ofcontact. This voltage is applied to the non-inverting input of amplifier1851. A high input impedance to amplifier 1851 is desirable to providegood accuracy in determining the contact point. Amplifier 1851 isconstructed from field effect transistors which require very little biascurrent so the resistance of the X coordinate sheet 1881 will notcontribute an appreciable error. Amplifier 1851 drives its invertinginput to the potential of its non-inverting input through capacitor1860. This causes its output initially to equal the voltage present atits non-inverting input. The level of signal DOUT at the output ofamplifier 1852 goes to a high state because its non-inverting input,driven by amplifier 1851, will be above its inverting input which isconnected to VREFL. Signal DOUT remains high until the conclusion of thePCA period (FIG. 16). The voltage present at the non-inverting input ofamplifier 1851 will appear across resistor 1857 until the PMA periodcompletes. This causes a current proportional to position of the contactwith the Y coordinate sheet 18.82 to flow into capacitor 1860. Theoutput of amplifier 1851 ramps positively to maintain its invertinginput at the same potential as its non-inverting input. At theconclusion of the PMA time, capacitor 1860 has a charge proportional tothe position of contact with the Y coordinate sheet 18.82 and the lengthof time of the PMA phase.

[0609] When the active ZERO signal is received into digital controllerblock 1802, QSADC module 1211a switches into the conversion cycle (PCA)for the voltage at Port X. At the start of the conversion cycle, up/downcounter 1803 switches to count increment mode (note that the countervalue is already zero). The number of count increments required for theDOUT pin (i.e., output terminal of analog comparator 1852) to return toa low voltage is directly proportional to the ratio of the voltagemeasured at the Port Y to the reference voltage VREFH.

[0610] Conversion is completed by setting switch positions as depictedin FIG. 51H. The non-inverting input of amplifier 1851 is connected toVREFL through switch 1853 e. Amplifier 1851 will drive its invertinginput to VREFL through capacitor 1860. This causes VREFL to be appliedto one side of resistor 1857 with VREFH applied to the other throughswitch 1853 k. This causes a current proportional to VREFL minus VREFHacross resistor 1857 to flow out of capacitor 1860. It should be notedthat the current flowing during the PCA phase is the same magnitude (butreversed in sign) as the current flowing during the PMA phase if thepoint of contact is at the end of the sheet connected to VREFH. To theextent that the point of contact is closer to the end connected to VREFLthe PMA current will be proportionately less. The output of amplifier1851 will ramp negatively to maintain its inverting input at the samepotential as its non-inverting input. The PCA phase concludes when theoutput of amplifier 1851 crosses below VREFL, the potential present atthe inverting input of amplifier 1852, at which time DOUT will fall to alow state. The transition of DOUT marks the termination of the PCA. Thelength of time in the PCA phase divided by the length of time in theprevious state will be proportional to the point of contact. When thetimes are equal (i.e., the ratio is one), the point of contact was atthe VREFH end of the sheet. If the ratio is one half, the point ofcontact is half way between the VREFH and VREFL ends of the sheet. Ifthe ratio is zero (time in PCA phase is zero), the point of contact isat the VREFL end of the sheet. After the end of PCB phase has beenrecognized, digital controller block 1802 transfers the count in up/downcounter 1803, which represents a digital value of the voltage at Port X,to register 1805 (REGY), and the circuit again enters the MeasurementInitial State to prepare for the next measurement.

[0611] Similarly, referring to FIG. 51I, a conversion to read theposition of contact with the X coordinate sheet (18.81 in a four-contactimplementation) connects VREFH to RHT (18.86) of the X coordinate sheetand VREFL to LFT (18.85) of the X coordinate sheet. The SEL signal isLOW. At the point of contact with the Y coordinate sheet, a voltage isdeveloped which is proportional to the X coordinate of the point ofcontact. This voltage is applied to the non-inverting input of amplifier1851. The operation of amplifiers 1851 and 1852 is identical to thatdescribed previously for the PMA phase for the Y direction. At theconclusion of the PMB time, capacitor 1860 has a charge proportional tothe position of contact with the X coordinate sheet and the length oftime of the PMB phase.

[0612] Similarly, conversion is completed by setting switch positions asdepicted in FIG. 51J. The non-inverting input of amplifier 1851 isconnected to VREFL through switch 1853 e. The operation of amplifiers1851 and 1852 is identical to that described previously for the PCAphase in the Y direction. After the end of PCB phase has beenrecognized, digital controller block 1802 transfers the count in up/downcounter 1803, which represents a digital value of the voltage at Port Y,to register 1804 (REGX), and the circuit again enters the MeasurementInitial State to prepare for the next measurement.

[0613] Similarly, referring to FIG. 51K, a conversion to read thevertical position of contact with the X-Y coordinate sheet (in afive-contact implementation) connects VREFH to TOP (18.97) of the X-Ycoordinate sheet 18.93 and VREFL to BOT (18.98) of the X-Y coordinatesheet (18.93). Note the SEL signal is HIGH. At the point of contact withthe contact sheet 18.92 a voltage is developed which is proportional tothe Y coordinate of the point of contact. This voltage is applied to thenon-inverting input of amplifier 1851 through switches SEL 1853 p andMEAS 1853 n wherein the contact MID has been connected to connection18.96 of contact sheet 18.92. The operation of amplifiers 1851 and 1852is identical to that described previously for the PMA phase for the Ydirection. At the conclusion of the PMA time, capacitor 1860 has acharge proportional to the position of contact with the Y coordinatesheet 18.93 and the length of time of the PMB phase

[0614] Similarly, conversion is completed by setting switch positions asdepicted in FIG. 51L. Note that SEL is now LOW. The non-inverting inputof amplifier 1851 is connected to VREFL through switch 1853 e. Theoperation of amplifiers 1851 and 1852 is identical to that describedpreviously for the PCA phase in the Y direction. After the end of PCAphase has been recognized, digital controller block 1802 transfers thecount in up/down counter 1803, which represents a digital value of thevoltage at the MID port, to register 1805 (REGY), and the circuit againenters the Measurement Initial State to prepare for the nextmeasurement.

[0615] Referring to FIG. 51M, a conversion to read the horizontalposition of contact with the X-Y coordinate sheet (in a five-contactimplementation) connects VREFH to LHT (18.94) of the X-Y coordinatesheet and VREFL to RHT (18.95) of the X-Y coordinate sheet. Note the SELsignal is HIGH. At the point of contact with the contact sheet 18.92 avoltage is developed which is proportional to the X coordinate of thepoint of contact. This voltage is applied to the non-inverting input ofamplifier 1851 through switches SEL 1853 p and MEAS 1853 n wherein thecontact MID has been connected to connection 18.96 of contact sheet18.92. The operation of amplifiers 1851 and 1852 is identical to thatdescribed previously for the PMA phase for the Y direction. At theconclusion of the PMA time, capacitor 1860 has a charge proportional tothe position of contact with the X coordinate sheet and the length oftime of the PMB phase Similarly, conversion is completed by settingswitch positions as depicted in FIG. 51N. Signal SEL is now LOW. Thenon-inverting input of amplifier 1851 is connected to VREFL throughswitch 1853 e. The operation of amplifiers 1851 and 1852 is identical tothat described previously for the PCA phase in the Y direction. Afterthe end of PCB phase has been recognized, digital controller block 1802transfers the count in up/down counter 1803, which represents a digitalvalue of the voltage at the MID port, to register 1804 (REGX), and thecircuit again enters the Measurement Initial State to prepare for thenext measurement.

[0616]FIG. 51 is a block diagram showing interface signals of QSADCmodule 1211 b in another implementation. The implementation of FIG. 51is similar to the implementation in FIG. 17 and therefore the discussionfor similar features will not be repeated. Table 1 provides a briefdescriptive summary of the signals shown in FIG. 51.

[0617] The implementation of FIG. 51 includes a digital interface 1902.4that is different than digital interface 1702 (FIG. 17). Specifically,digital interface 1902.4 comprises one 8-bit output bus 1902 a.4(labeled DOUT[7:0]) and a Select signal 1902 b.4 (labeled SEL), ratherthan output buses 1702 a and 1702 b as described in reference to FIG.17. Output bus 1902 a.4 provides the results of the analog-to-digitalconversion (ADC) process of the voltage at the port A or the port B withrespect to the voltage reference VREF.

[0618] Select signal 1902 b.4 is the output select signal that selectswhether to present the results from the port A or the port B after theDONE signal is asserted. For example, if SEL 1902 b.4 is a logical LOWlevel, then the ADC result of the voltage at the port A is presented onoutput bus 1902 a.4. Otherwise, if select signal 1902 b.4 is a logicalhigh level, then the ADC result of the voltage at the port B ispresented on output bus 1902 a.4. TABLE 1 Signal/Pin Description PinName Type Description AMAX Bidirectional Maximum Analog Measurement Pinfor the A Port AMIN Bidirectional Minimum Analog Measurement Pin for theA Port BMAX Bidirectional Maximum Analog Measurement Pin for the B PortBMIN Bidirectional Minimum Analog Measurement Pin for the B Port STARTInput Start Conversion Pin Active HIGH CLK Input Clock RSTN Input ResetActive LOW PDN Input Power Down Control Active LOW DOUT[7:0] OutputDigitized Bus for Measured Value DONE Output Done Pin Active HIGH CONTOutput Continuity Detection Pin Active HIGH VREF Input Analog VoltageReference AVD Power Analog Power AVS Power Analog Ground VDD PowerDigital Power VSS Power Digital Ground

[0619]FIG. 51A and FIG. 51B show another implementation of QSADC module1211 b, in accordance with the present invention. FIG. 51A and FIG. 51Bare similar to FIG. 18 and FIG. 18A and operate in a similar fashionand, therefore, only basic operational differences between theembodiments will be specifically noted.

[0620]FIG. 51A is a top-level block diagram of QSADC module 1211 b,including an analog block 2001.4, a digital controller block 2002.4, apre-settable up/down counter block 2003.4, registers 2004.4 and 2005.4,a NAND gate 2006.4, and a multiplexer 2007.4. FIG. 51A differs from FIG.18 due mainly to the addition of select signal 1902 b.4 (labeled SEL) inFIG. 51A. Select signal 1902 b.4 employs multiplexer 2007.4 to selectthe data stored in register 2004.4 or register 2005.4 to be provided onoutput bus 1902 a.4 (DOUT[7:0]). For example, the digital conversionresults of the voltages at the port A and the port B are stored inregister 2004.4 and register 2005.4, respectively. If SEL 1902 b.4 is ata logical low level, the conversion results of the port A (stored inregister 2004.4) are provided on output bus 1902 a.4 via multiplexer2007.4. If SEL 1902 b.4 is at a logical high level, the conversionresults of the port B (stored in register 2005.4) are provided on outputbus 1902 a.4 (DOUT[7:0]) via multiplexer 2007.4.

[0621]FIG. 51B shows an implementation of analog block 2001.4 of FIG.51A. The operation of the implementation shown in FIG. 51B is similar tothe operation of the implementation shown in FIG. 18A and, therefore,the discussion will not be repeated except for noting generaldifferences.

[0622] As shown in FIG. 51B, analog block 2001.4 includes a digitalcontrol block (DCNTL) 2020.4 and a level shift circuit 2022.4.Initially, QSADC module 1211 b is in sleep mode, but checking forelectrical continuity between the ports A (AMAX and AMIN) and B (BMAXand BMIN), with a sleep control signal (SLP) at a logic high, a powerdown signal (PDON) at a logic low, and operational amplifier 1851 andanalog comparator 1852 powered down to conserve power. In this mode ofoperation, switches 1853 c, 1853 b, 1853 h, 1853 i, 1853 l, 1853 n, and1853 f (i.e., signals A0, A2, B1, B2, MEAS, and SLP) are closed, whileall other switches are open.

[0623] When there is no electrical continuity between the ports Y and X,a continuity out (CONT) signal is at a logical low level. Whenelectrical continuity is established, the input to level shift circuit2002.4 is pulled to a high voltage (i.e., to a voltage level of thevoltage reference) and the continuity out signal transitions to alogical high level. The logical high on the continuity out signal isdetected (and de-bounced) by a flip flop (not shown) in digitalcontroller block 2002.4, resulting in digital controller block 2002.4asserting a logical high signal on the CONT terminal. QSADC module 1211b then exits the sleep mode and proceeds to power up operationalamplifier 1851 and analog comparator 1852 to begin the primary mode ofoperation (as discussed above). During the primary mode, the circuitryassociated with the continuity checking in digital controller block2002.4 may be disabled.

[0624]FIG. 51C illustrates a block diagram showing exemplary interfacesignals for another implementation. The block diagram illustrates adigital logic wrapper mixed-signal macro (also referred to as a touchscreen interface or TSI) that encapsulates QSADC 1211 a. The wrapperprovides an interface to the 8051 micro-controller in central processingmodule (SYS) 1205 for reading the touch screen coordinate data fromQSADC 1211 a.

[0625] The wrapper contains data, control, and status registers, asdescribed in further detail below, that allow the software driver towork more efficiently by presenting the necessary information inspecific locations. An internal state machine in the wrapper will managethe operation of QSADC 1211 a and its interaction with touch screeninterface 1211.

[0626] Touch screen interface 1211 uses the three interfaces AIO 1701,power supply interface (PSI) 1703, and DI 1702. AIO 1701 and powersupply interface 1703 are as described above, while DI 1702 alsoincludes signals required by central processing module (SYS) 1205 tocontrol the operation of QSADC 1211 a and access the sampled data. Thesesignals include a SYS_CLK signal 5002.4, a TS_SFR_REG_EN signal 5010.4,a SFR_ADDR[7:0] signal 5012.4, a SFR_DATA_OUT[7:0] signal 5014.4, aSFR_WR_N signal 5016.4, a SFR_RD_N signal 5018.4, a TS_SFR_DATA_IN[7:0]signal 5042.4, a TS_MEM_REG_EN signal 5020.4, a MEM_ADDR[2:0] signal5022.4, a MEM_DATA_OUT[7:0] signal 5024.4, a MEM_WR_N signal 5026.4, aMEM_RD_N signal 5028.4, a TS_MEM_DATA_IN[7:0] signal 5040.4, a TS_INTsignal 5044.4, and a QSADC_CLK signal 5004.4.

[0627] RSTN signal 5000.4 is the chip-level reset used to initialize theinternal logic of the TSI. SYS_CLK signal 5002.4 is the clock used tosynchronize the TSI's internal logic to central processing module (SYS)1205. QSADC_CLK signal 5004.4 is the clock used to control touch screeninterface 1211 state machine and QSADC 1211 a. TS_SFR_REG_EN signal5010.4 indicates that touch screen interface 1211 register on the SFRbus, a component of central processing module (SYS) 1205, is about to beaccessed. The SFR bus enables access to non-memory mapped registers, asdescribed elsewhere herein.

[0628] SFR_ADDR[7:0] signal 5012.4 is the address received from the 8051used to access one of the SFR registers. SFR_DATA_OUT[7:0] signal 5014.4contains the data (i.e. control word) to be written into the registers.SFR_WR_N signal 5016.4 is used in conjunction with TS_SFR_REG_EN signal5010.4 to write TS_SFR_DATA_IN[7:0] signal 5042.4 to one of theregisters addressed by SFR_ADDR[7:0] signal 5012.4. SFR_RD_N signal5018.4 is used in conjunction with TS_SFR_REG_EN signal 5010.4 to readSFR_DATA_OUT[7:0] signal 5014.4 from one of the registers addressed bySFR_ADDR[7:0] signal 5012.4. TS_SFR_DATA_IN[7:0] signal 5042.4 containsthe data (i.e. data/status words) to be read from the registers.

[0629] TS_MEM_REG_EN signal 5020.4 indicates that a TSI register on theMemory Mapped I/O (MMIO) bus, a component of central processing module(SYS) 1205 is about to be accessed. MEM_ADDR[2:0] signal 5022.4 is theaddress coming from the 8051 used to access one of the MMIO registers.This address bus is a partial decode of the 16-bit MEM_ADDR[2:0] signal5022.4 on the 8051 (specifically bits [2:0]). All MMIO registertransactions are qualified with the TS_MEM_REG_EN signal 5020.4. Using apartial decode reduces routing congestion and eliminates the need for afull decode.

[0630] MEM_DATA_OUT[7:0] signal 5024.4 contains the data (i.e. controlword) to be written into the registers. MEM_WR_N signal 5026.4 is usedin conjunction with TS_MEM_REG_EN signal 5020.4 to writeTS_MEM_DATA_IN[7:0] signal 5040.4 data to one of the registers addressedby MEM_ADDR[2:0] signal 5022.4. MEM_RD_N signal 5028.4 is used inconjunction with TS_MEM_REG_EN signal 5020.4 to read MEM_DATA_OUT[7:0]signal 5024.4 from one of the registers addressed by MEM_ADDR[2:0]signal 5022.4. TS_MEM_DATA_IN[7:0] signal 5040.4 contains the data (i.e.data/status words) to be read from the registers.

[0631] TS_INT signal 5044.4 is an interrupt line sent to the 8051contained within central processing module (SYS) 1205 to indicate thatan (X, Y) coordinate pair has been converted to a digital value by QSADC1211 a and is ready for use. The 8051 treats this line as anedge-sensitive interrupt, with the line remaining high until the 8051clears it. TABLE 1.6.6a Signal Type Description Source Destination RSTNInput Global chip reset QSADC_CLK Input QSADC 1211a macro clock CLKGENSYS_CLK Input SYS 1205 module clock CLKGEN AIO Interface AIO PSIInterface AIO TS_SFR_REG_EN Input Enables touch screen SFR SYS 1205register SFR_ADDR[7:0] Input SFR address from 8051 SYS 1205SFR_DATA_OUT[7:0] Input SFR data from 8051 SYS 1205 SFR_WR_N Input SFRdata write enable SYS 1205 SFR_RD_N Input SFR data read enable SYS 1205TS_SFR_DATA_IN[7:0] Output SFR data to 8051 SYS 1205 TS_MEM_REG_EN InputEnable touch screen MEM SYS 1205 register MEM_ADDR[2:0] Input MMIOaddress from 8051 SYS 1205 MEM_DATA_OUT[7:0] Input MMIO data from 8051SYS 1205 MEM_WR_N Input MMIO data write enable SYS 1205 MEM_RD_N InputMMIO data read enable SYS 1205 TS_MEM_DATA_IN[7:0] Output MMIO data to8051 SYS 1205 TS_INT Output Interrupt to 8051 SYS 1205 indicating an (X,Y) coordinate pair is ready for reading.

[0632]FIG. 51D shows a flowchart for performing diagnostics for the TSIand FIG. 51E shows a functional block diagram corresponding to the TSI.In FIG. 51E, besides QSADC 1211 a, various registers are shown,including a TSI_CTRL[7:0] register 5062.4, an SMP_DELAY[7:0] register5060.4, an INT_STAT[7:0] register 5064.4, an X_DATA[7:0] register5066.4, and a Y DATA[7:0] register 5068.4.

[0633] Specifically, TSI_CTRL[7:0] 5062.4 controls the operation oftouch screen interface 1211 and QSADC 1211 a. Bit 0 of TSI_CTRL[7:0]5062.4 enables or disables the TSI. If this register bit is ‘0’, aninternal state machine (FSM) 5070.4 stays in IDLE and QSADC 1211 a is inlow-power mode. If this register bit is ‘1’, the state machine startscollecting samples as soon as it detects activity on the touch screen.Bit 1 of TSI_CTRL[7:0] 5062.4 indicates the type of touch screen that isattached to the Power Meister (E.G., 4-pin or 5-pin).

[0634] SMP_DELAY[7:0] register 5060.4 controls the time between samples.For example, QSADC 1211 a is capable of collecting a pair of (X, Y)coordinate samples every 3.9 ms given a 262.144 kHz clock. However, thisrate may be too fast for certain operating systems to handle, soSMP_DELAY[7:0] register 5060.4 allows the TSI to vary the waiting timebetween successive samples from 0 ms to 6.4 ms. The maximum samplecollection rate would then be 3.9 ms to 10.3 ms respectively.

[0635] INT_STAT[7:0] register 5064.4 is the interrupt status register.When an interrupt is detected, TSI_INT signal 5044.4 is held high untilthe 8051 clears the particular interrupt.

[0636] A DIAG_CTRL[7:0] register (not shown) controls the diagnosticlogic and is routed directly to the QSADC 1211 a block via the MMIO bus.In this mode, internal state machine 5070.4 is bypassed and QSADC 1211 ais directly under software control. The 8051 will set the DIAG_CTRL[1]bit to ‘1’ to reset the logic and the TSI will then clear this bit. Whenthe 8051 sets the DIAG_CTRL[2] bit to ‘1’, QSADC 1211 a retrieves 1sample pair. The 8051 polls the DIAG_CTRL[5] bit to determine when asample is available for reading.

[0637] X_DATA[7:0] register 5066.4 contains X coordinate data from thetouch screen. QSADC 1211 a latches X coordinate data into this registerand asserts DONE signal 1702 c, which is then sent as an interrupt lineto central processing module (SYS) 1205 to allow the software driver toread the data.

[0638] Y_DATA[7:0] register 5068.4 contains Y coordinate data from thetouch screen. QSADC 1211 a latches Y coordinate data into this registerand asserts DONE signal 1702 c, which is then sent as an interrupt lineto central processing module (SYS) 1205 to allow the software driver toread the data. Table 1.6.6b summarizes information for the variousregisters. TABLE 1.6.6b Register Name Address Type AddressingDescription TSI_CTRL[7:0] R/W MMIO Controls the operation of the TSI[7:6] - undefined [1] - touch screen mode select 0 = 4-pin 1 = 5-pin[0] - TSI enable (0 - disable, 1 - enable) SMP_DELAY[7:0] R/W MMIOSample delay [7:6] - undefined [5:0] - sample delay in increments of 100us (0x00 = no delay, 0x3F = 6.4 ms) INT_STAT[7:0] R/W SFR InterruptStatus Register [7:6] - undefined [5] - conversion underrun error [4] -conversion overrun error [3] - undefined [2] - data ready [1] - pen down[0] - pen up DIAG_CTRL[7:0] R/W MMIO Diagnostic Control and Status[7:6] - undefined [5] - data ready [4] - QSADC ready [3] - undefined[2] - start single conversion [1] - reset TSI (set by 8051, cleared byTSI) [0] - diagnostic mode enable X_DATA[7:0] R SFR 8-bit X coordinatedata from the touch screen Y_DATA[7:0] R SFR 8-bit Y coordinate datafrom the touch screen

[0639] In terms of general operation, the 8051 will set bit 0 (i.e.,TSI_CTRL[0]) of TSI_CTRL[7:0] register 5062.4 to ‘1’ to enable the TSIafter the chip (i.e., switching power supply controller 1200) has beenpowered up and the global chip reset has been asserted. When touchscreen interface 1211 is enabled, internal state machine 5070.4 willretrieve (X, Y) sample pairs as long as QSADC 1211 a has detectedcontinuity (i.e. a pen-down condition exists). After QSADC 1211 a hascollected a sample pair, it will wait for a specified amount of time, asindicated by SMP_DELAY[7:0] register 5060.4, before starting over andcollecting the next sample pair. This cycle continues as long ascontinuity is detected by QSADC 1211 a.

[0640] Internal state machine (FSM) 5070.4 schedules the conversion oftouch screen data by toggling START/RSTN signal 1702 e of QSADC 1211 aand then sampling DONE signal 1702 c to load X/Y data registers 5066.4and 5068.4. The sampling will occur periodically as long as CONT signal1702 d of QSADC 1211 a is asserted.

[0641] Every time a sample is collected or a pen-down/pen-up conditionis detected (as seen by a toggling of the CONT 1702 d signal), aninterrupt is sent to the 8051. This interrupt line is held high untilthe 8051 clears the corresponding bit in INT_STAT[7:0] register 5064.4.An interrupt is also sent if a buffer overrun/underrun condition occurs.The TSI double-buffers the X/Y coordinate samples and the activity onthese buffers is tracked to generate the appropriate interrupt.

[0642] Referring to FIG. 51D and FIG. 51E, when the TSI is placed indiagnostic mode by setting DIAG_CTRL[4] of DIAG_CTRL[7:0] register5062.4 to ‘1’, FSM 5070.4 is bypassed and START/RSTN signal 1702 e ofQSADC 1211 a is directly controlled by setting bit 5 of DIAG_CTRL[7:0]register 5062.4. This mode of operation is intended for use as a debugmechanism to verify the operation of the TSI and QSADC 1211 a.Interrupts to the 8051 are disabled and a polling mechanism is usedwhere bit 1 (i.e., INT_STAT[1]) of INT_STAT[7:0] register 5064.4 acts asDONE signal 1702 c.

[0643] The test routine shown in FIG. 51D is as follows. The 8051 (step5050.4) reads DIAG_CTRL[4] to ensure QSADC 1211 a is ready. If QSADC1211 a is not ready, the 8051 must first assert DIAG_CTRL[1] to resettouch screen interface 1211 and QSADC 1211 a. The 8051 sets DIAG_CTRL[2]to ‘1’, then the 8051 polls DIAG_CTRL[5] until TRUE. When TRUE, 8051reads the values (5054.4) in X_DATA[7:0] register 5066.4 and Y_DATA[7:0]register 5068.4. Following a WAIT period (5056.4), the flow returns toIDLE (step 5058.4) and repeats as necessary.

[0644] Several advantages compared to the prior art may be seen. Theinvention eliminates sensitivity to noise. The most difficult noisesource in a PDA application is the high voltage, high frequency a.c.signal that drives the CCFL or other type of backlight. By arrangingclock frequencies such that there is always an even number of backlightpulses during a conversion period (e.g., 1601+1602 of FIG. 16) any noisethat is picked up from one backlight half cycle is subtracted back outby the next half cycle. Since all clocks are controlled by switchingpower supply controller 1200, this may be arranged. In addition, thesystem does not drift due to component aging or thermal effects nor doesit require calibration, either at the time of manufacture or later.Also, the invention does not require precision components (typicallyresistors and capacitors) in that the same resistor and capacitor areused during the measurement and the conversion phases. Thus any “errors”in component value during 1601 or 1602 times (FIG. 16) are reversedduring 1605 and 1606 times.

[0645] Quad-Slope Analog to Digital Converter (QSADC) module 1211includes a custom low-power mixed-signal circuit that has both analogand digital input and output signals, including analog and digital powerand ground reference voltages. QSADC module 1211 measures and digitizes,to 8 bits of resolution, the voltages at two separate external portsrelative to a voltage reference VREF. The maximum conversion rate atQSADC module 1211 is approximately 300 sps (samples per second). FIG. 16is a timing diagram illustrating the quad-slope (i.e., dual conversion)analog to digital conversion (ADC) operations carried out in the QSADCmodule 1211.

[0646] As shown in FIG. 16, time intervals 1601 and 1602 (i.e.,“measurement periods” PMA and PMB) are equivalent fixed time durationscorresponding to 256 counts of a reference timer or counter. During timeperiods 1601 and 1602, the positive slopes if signal trace segments 1603and 1604 reaches voltages·V_(A) and V_(B), represent signals beingmeasured at the analog A and B ports of the QSADC module 1211 over timeperiods 1601 and 1602. During time intervals 1605 and 1606 (“conversionperiods” PCA and PCB), signal trace segment 1607 and 1608 have identicalnegative slopes, tracing in voltage declines from voltages V_(A) andV_(B) to zero. During these conversion periods, the numerical countsrepresent direct analog to digital conversions of the measured voltagesV_(A) and V_(B). At the completions of the conversion periods,end-of-conversion (EOC) pulses are provided (e.g., at times t₁ and t₂)to signal the end of each analog to digital conversion and to reset andcalibrate the analog circuitry in QSADC module 1211 for subsequentconversions.

[0647]FIG. 17 is a block diagram showing the interface signals of QSADCmodule 1211 in one implementation. As shown in FIG. 17, QSADC module1211 includes: (a) analog measurement interface (AMI) 1701, digitalinterface (DI) 1702, and the power supply interface 1703. Analogmeasurement interface (AMI) comprises analog bi-directional measurementterminals 1701 a and 1701 b of port A (i.e., terminals AMAX and AMIN),analog bi-directional measurement terminals 1701 c and 1701 d of port B(i.e., terminals BMAX and BMIN) and reference voltage signal 1701 e(i.e., reference voltage VREF).

[0648] Analog measurement interface 1701 operates in two modes in eachterminal of each port. In a first mode (“primary mode”), terminal 1701 a(AMAX) measures two independent external voltages relative to voltagereference VREF at terminal 1701 e. The primary mode includes two phases.During the first phase, terminals 1701 a and 1701 b (i.e., AMAX and AMINterminals) are shorted to allow port A to float and to complete thefirst digital voltage conversion (at the port A). During the secondphase, terminal 1701 a (i.e., terminal AMAX) is connected to terminal1701 e, which carries reference voltage VREF, to facilitate the seconddigital voltage conversion (at port B). In a second mode (“low power”)terminals 1701 a and 1701 b (i.e., AMAX and AMIN terminals) are againshorted to allow port A to float. During low power, port A and port Boperate to check for electrical continuity between these ports.

[0649] In the primary mode, terminal 1701 b measures two independentexternal voltages with respect to a voltage reference, VREF. In theprimary mode, the first phase for terminal 1701 b is shared with thecorresponding first phase for terminal 1701 a, as described above. Inthe second phase of the primary mode, terminal 1701 b connects to analogground reference (AVS) at terminal 1703 d to facilitate the seconddigital voltage conversion (at port B). The operations of terminal 1701b's low power are the same as those of terminal 1701 a under low power.

[0650] Similarly, in the primary mode, terminal 1701 c (BMAX) measurestwo independent external voltages relative to voltage reference VREF atterminal 1701 e. During a first phase, terminals 1701 c and 1701 d(i.e., BMAX and BMIN terminals) are shorted to allow port B to float andto complete the second digital voltage conversion (at the port B).During the second phase, terminal 1701 c (i.e., terminal BMAX) isconnected to terminal 1701 e, which carries reference voltage VREF, tofacilitate the second digital voltage conversion (at port A). In asecond mode (“low power”) terminals 1701 c and 1701 d (i.e., BMAX andBMIN terminals) are again shorted to allow port B to float. During lowpower, port A and port B operate to check for electrical continuitybetween these ports.

[0651] In the primary mode, terminal 1701 d measures two independentexternal voltages with respect to a voltage reference, VREF. In theprimary mode, the first phase for terminal 1701 d is shared with thecorresponding first phase for terminal 1701 c, as described above. Inthe second phase of the primary mode, terminal 1701 d connects to analogground reference (AVS) at terminal 1703 d to facilitate the firstdigital voltage conversion (at port A). The operations of terminal 1701d's low power are the same as those of terminal 1701 c under low power.

[0652] Digital interface 1702 comprises 8-bit output buses 1702 a(AOUT[7:0]) and 1702 b (BOUT[7:0]) for displaying digital results of theconversions at ports A and B, respectively, completion or “DONE” signal1702 c, continuation detection or “CONT” signal 1702 d, start conversionor “START” signal 1702 e, 128 KHz 50% duty cycle reference clock signal(“CLK”) 1702 f, asynchronous reset signal (“RSTN”) 1702 g, andpower-down signal (“PDN”) 1702 h. START is the start control pin used toinitiate the analog to digital conversion processes. When the START pingoes HIGH the processing starts and subsequent conversions will not beinitiated until the START pin toggles LOW then HIGH again.

[0653] The DONE signal at terminal 1702 c is asserted when the digitalconversions at both ports A and B are completed, to signal that resultscan be read from output buses 1702 a and 1702 b (i.e., AOUT and BOUTbuses). The CONT signal indicates detection of continuity at ports A andB.

[0654] Power supply interface 1703 comprises analog power and groundreference signals 1703 a and 1703 b (i.e., analog power and groundreference signals AVD and AVS), and digital power and ground referencesignals 1703 c and 1703 d (i.e., digital power and ground referencesignals VDD and VSS).

[0655]FIG. 18 and FIG. 18A show one implementation of QSADC module 1211,in accordance with the present invention. FIG. 18 is a top-level blockdiagram of QSADC module 1211, including analog block 1801, digitalcontroller block 1802, presettable up/down counter block 1803, 8-inputNAND gate 1806, and 8-bit Registers 1804 and 1805 (i.e., registers REGAand REGB). FIG. 18A shows one implementation of analog block 1801 ofFIG. 18. As shown in FIG. 18A, analog block 1801 includes operationalamplifier 1851 and analog comparator 1852, in addition to MOStransmission gates 1853 a to 1853 m, inverter 1854 and digital controlblock (DCNTL) 1855. DCNTL block 1855 generates the control signalsnecessary to control the MOS transmission gates 1853 a to 1853 m. Thecommon mode ranges of the operational amplifier 1851 and analogcomparator 1852 are rail to rail (i.e., 0 to 3.3V). For convenience theMOS transmission gates 1853 a to 1853-m are referred to as “switches”and each switch is designated by its control input signal (i.e., A0-A3,B0-B3, MEAS, SLP, EOC, CONV). Initially, QSADC module 1211 is in lowpower, where electrical continuity between port A (i.e., terminals 1701a (AMAX) and 1701 b (AMIN)) and port B (i.e., terminals 1701 c (BMAX)and 1701 d (BMIN)) is checked. Under low power, switches 1853 b, 1853 c,1853 h and 1853 i, 1853 d, 1853 l, and 1853 f (i.e., signals A0, A2, B1,B2, MEAS and SLP) are closed, while all other switches are open. Whenthere is no electrical continuity between ports A and B, the outputvoltage of operational amplifier 1851 is a low voltage, and the outputvoltage of analog comparator 1852 is also a low voltage. When electricalcontinuity is established between ports A and B, the output terminal ofswitch 1853 d (i.e., the non-inverting input terminal of operationalamplifier 1851) is pulled to a high voltage, so that the output terminalof analog comparator 1852 is at a high voltage. The output terminal ofanalog comparator 1852 is the “DOUT” terminal of analog block 1801 (FIG.18), which is connected to the “DIN” terminal of digital control block1802. In response to the high voltage at the output terminal of analogblock 1801, the CONT terminal (i.e., terminal 1702 d at FIG. 17) isdriven to a high voltage, resulting in QSADC module 1211 exiting the lowpower, and entering the primary mode.

[0656] In primary mode, entered when the CONT signal is at a highvoltage, when an active START signal at terminal 1702 e is received,digital control block 1802 begins a measurement cycle of the voltage atport A by presetting up/down counter 1803 to hexadecimal FF (i.e., FFh),thereby resetting the CONT signal, and beginning the measurement andconversion process. Thereafter, each rising edge of the CLK signal atterminal 1702 f decrements up/down counter 1803 until the count reacheszero (for a total of 256 counts), which is decoded by NAND gate 1806 toactivate the ZERO signal received into digital control block 1802.

[0657] During the measurement cycle of port A, switches 1853 b, 1853 c,1853 h and 1853 i, 1853 d, 1853 l, and 1853 f (i.e., signals A0, A2, B1,B2, MEAS) are closed, and all other switches are open. As operationalamplifier 1851 is configured as an integrator with capacitor 1856, aspecific charge approximately proportional to the voltage at port A isaccumulated across capacitor 1856 over the time interval correspondingto 256 count decrements of up/down counter 1803.

[0658] When the active ZERO signal is received into digital controllerblock 1802, QSADC module 1211 switches into the conversion cycle for thevoltage at port A. At the start of the conversion cycle, up/down counter1803 switches to count increment mode. During the conversion cycle, theswitches 1853 e and 1853 k controlled by the CONV signal are closed,while all other switches are open, so that the charge on capacitor 1856discharges reference resistor 1857 (R0). Therefore, the number of countdecrements required for the DOUT pin (i.e., output terminal of analogcomparator 1852) to return to a low voltage is directly proportional tothe ratio of the voltage measured at the port A to the reference voltageVREF. The conversion cycle terminates when the high to low voltagetransition occurs at analog comparator 1852, and detected by digitalcontroller block 1802 at the terminal carrying signal DIN. At this time,digital controller block 1852 transfers the count in up/down counter1803, which represents a digital value of the voltage at port A, toregister 1804. At this time, digital controller 1802 closes and opensswitch 1853 n via control signal EOC, to compensate any voltage offsetacross capacitor 1856, so as to ready QSADC module 1211 for a subsequentport B measurement and conversion cycle. The measurement and conversioncycles for port B are substantially the same as that described above forthe port A. The result of a port B conversion cycle is stored inregister 1805 (REGB). The DONE signal (terminal 1702 c) is then assertedand QSADC module 1211 returns to sleep mode, until the next assertedSTART signal (terminal 1702 e) is received, or when electricalcontinuity is detected across ports A and B.

[0659] While several embodiments of this invention have been shown,other embodiments of this invention will be obvious to those skilled inthe switching power supply design arts.

We claim:
 1. A sample and hold circuit comprising: a first input circuitadapted to sample and hold a plurality of first voltage measurements; asecond input circuit, coupled to the first input circuit, adapted tosample and hold a plurality of second voltage measurements correspondingto current measurements; and a multiplexer, coupled to the first inputcircuit and the second input circuit, adapted to selectively provide amultiplexer output signal corresponding to one of the first voltagemeasurements or the second voltage measurements.
 2. The circuit of claim1, further comprising a voltage divider circuit, coupled between thefirst input circuit and the multiplexer, adapted to scale the firstvoltage measurements.
 3. The circuit of claim 1, wherein the secondinput circuit further comprises a multiplier circuit adapted to multiplythe second voltage measurements.
 4. The circuit of claim 3, wherein themultiplier circuit comprises a switched capacitor network.
 5. Thecircuit of claim 1, wherein the multiplexer provides the multiplexeroutput signal to an analog-to-digital converter.